Why can’t we define 'necessary' tighter, by making it include empirical evidence of such a statement?
Everything that is agreed to be necessarily can be empirically verified. For example, if we put two twos together, we get 4, and we can empirically verify this by putting two sets of 2 sweets together and getting four.
Even for logical principles such as Ockham’s Razor it is possible for them to be empirically verified by looking at the evolution of different theories (for example the decline of Caloric due to its unnecessary multiplication of entities).
The definition for necessary truth would therefore be: (a tautology/analytic truth/sound deductive argument/intuition) + empirical evidence.
There have numerous arguable “sleight of the hand tricks” regarding necessary statements (such as the "God exists necessarily"/The Ontological argument, we arguably don't have empirical evidence for God's existence), but a lot of these arguments seem to succeed in proving necessary truth, however this is entirely unfounded as far as empirical evidence goes.
Obviously verificationism/logical positivism specified for a statement to be meaningful it must be empirically verifiable, but this definition would elevate this to necessary truth itself.
This would make far more sense as when we talk about necessary truth, we are saying it is more than contingent, and therefore to make it necessary we should at least try and prove its contingency before doing so.