I think it's technically correct that you're never entitled to an exact count (edit: of chips behind, not yet committed to the pot), you're entitled to enough information that you should be able to get by your opponent allowing you to see all chip stacks and high denom chips. If your opponent won't verbally answer the question, they should not be allowed to block or obstruct your vision of their chip stacks or high denom chips if you ask to see them.
I've asked this question many times at the table, but it's often when players sit with their hands or forearms in front of their chips, especially when they have cards in front of them, and have their hands guarding their cards and blocking their chips, or maybe they have a drink blocking their chips, etc.
Sometime I might ask 'how many chips do you have behind'
or sometimes ask 'can you move your hands so I can see how many chips you have',
or in cash games where a red $5 is the main chip, 'do you have any green (or black) (or high denom) chips'
Of course, I'm not really asking for an exact count. As players, especially when we're considering making a bet in a pot, we need to make sure be aware of what the opposing players have in their chip stack. (Are they a short stack who might jam? Do they have higher value chips that may be blocked from view? Etc.). Opposing players in games I've played in will typically always cooperate either answer verbally, move their hands/arms out of the way of their chips, push their higher denom chips to the front/top, or a combination thereof.
I agree; I'll give an answer. That said, on multiple occasions, I've seen Doyle Brunson announce to a table that he doesn't answer those questions. For whatever that's worth.
Indeed, Uncle Doyle wrote and said (including on camera) that it's rude to ask, provided that players' stacks are neat and countable.
He always stood for refusing to answer.
I've watched a whole lot of TV poker games where Doyle was playing, so I think I recall that if someone ever asked for his chip count, he'd at least move his hands/arms out of the way to give an opponent a clear and visible look at all his chips, and in cases where they played with cash bundles on Poker After Dark, where it may not have been clear how many bundles he had in front of him, I seem to recall him making those visible.