Why is it more rational to believe that other people are sentient rather than have no belief one way or the other?

[Sicnoo0]

I'm not talking about certainty; disproving solipsism is impossible, after all.
I'm talking about likelihood.

Any given organism is either sentient or not.

Why should I have any inclination to believe strongly one way or the other as to whether a given organism is sentient?
Why shouldn't I just remain entirely agnostic as to whether anyone is sentient or not?

If I'm 50/50 on whether or not others are sentient, then I will still treat others with kindness as though they are sentient, because there is a chance that they might in fact be sentient.

So it's not like being 50/50 on the matter would turn me into a horrible person as far as the consequences of my beliefs are concerned.

And it's not like any of that matters in the first place; a belief having bad consequences does not imply the belief is in disagreement with reality.

[FredVegrox]

It is better to act on the apparent sentience, instead of assuming the evidence of it is deceptive.