First, because they are "inconsequential". Nothing hangs on it for you, there is no need to act on them and accept the consequences also, it is a "cheap", easily swayable "acceptance". But this still leaves the question as to why accept rather than reject, as easily, perhaps at random.
Which brings us to the second because: they are not accepted without much evidence, there is plenty of evidence for them, in fact. It is just not processed into the conclusion consciously. They are inductive surmises from long ordinary experience condensed to a point where the inference made is subconscious. That people dislike being hit comes from observing people's reactions when they are, one's own empathy with the resulting pain, imagining it done to oneself, background knowledge about damage it might cause, etc. Same with people eating dinners, at least once in a while, or background knowledge about the whales and the moon, implied by mere familiarity with what the words mean. When such surmises are reflected upon their origin is colloquially labeled as "common sense".
Peirce thought a lot about what scholastics called logica utens, practical "implicit" logic. I'll quote his opinion on another famously accepted "inconsequential" claim, the one Descartes accepted so much as to believe it the indubitable foundation of all reasoning, upon which he tries to build chains of inferences leading to equally "indubitable" conclusions. It is his cogito, anticipated, to an extent, by Augustine. According to Peirce, "I think, therefore I am" is not an indubitable foundation, certain "in itself", but an instinctive surmise from a multitude of other less abstract ordinary acceptances. It is their intertwining with it, like strands in a cable, which holds it in place as "indubitable":
"There are, however, cases in which we are conscious
that a belief has been determined by another given belief, but are not conscious that it
proceeds on any general principle. Such is St. Augustine's "cogito, ergo sum." Such a
process should be called, not a reasoning, but an acritical inference.
[...] Descartes thought this "très-clair"; but it is a fundamental mistake to suppose
that an idea which stands isolated can be otherwise than perfectly blind. He professes
to doubt the testimony of his memory; and in that case all that is left is a vague
indescribable idea. There is no warrant for putting it into the first person singular. "I
think" begs the question. "There is an idea: therefore, I am," it may be contended
represents a compulsion of thought; but it is not a rational compulsion.
[...] Philosophy ought to... trust rather to the multitude and variety of its arguments than to the
conclusiveness of any one. Its reasoning should not form a chain which is no stronger
than its weakest link, but a cable whose fibers may be ever so slender, provided they
are sufficiently numerous and intimately connected." [quoted from Collected Papers of C. S. Peirce]
Another philosopher who famously reflected on our countless applications of common sense was Moore. In his Defence of Common Sense he gives many other examples of easily accepted truisms, not necessarily inconsequential, now called Moorean certainties:
"I begin, then, with my list of truisms, every one of which (in my own opinion) I know, with certainty, to be true... There exists at present a living human body, which is my body. This body was born at a certain time in the past, and has existed continuously ever since, though not without undergoing changes; it was, for instance, much smaller when it was born, and for some time afterwards, than it is now. Ever since it was born, it has been either in contact with or not far from the surface of the earth; and, at every moment since it was born, there have also existed many other things, having shape and size in three dimensions...
[...] Among the things which have, in this sense, formed part of its environment (i.e. have been either in contact with it, or at some distance from it, however great) there have, at every moment since its birth, been large numbers of other living human bodies... and many of these bodies have already died and ceased to exist. But the earth had existed also for many years before my body was born; and for many of these years, also, large numbers of human bodies had, at every moment, been alive upon it; and many of these bodies had died and ceased to exist before it was born".
Later he distilled it into a famous "hand argument":""I can prove now, for instance, that two human hands
exist. How?. By holding up my two hands, and saying, as I
make a certain gesture with the right hand "Here is one
hand" and adding, as I make a certain gesture with the left
"and here is another."". Wittgenstein was so taken by Moore's musings that he devoted his last work, On Certainty, to them. And he found some of Moore's truisms to be so consequential as to dub them hinge propositions, around which all other empirical reasoning revolves:
"That is to say, the questions that we raise and our doubts depend on the fact that some propositions are exempt from doubt, are as it were like hinges on which those turn.
But it isn't that the situation is like this: We just can't investigate everything, and for that reason we are forced to rest content with assumption. If I want the door to turn, the hinges must stay put." [OC 341,343]