I have asked for ID, but that is purely because the potential punter said they were 18/19, or turning it (punt as a birthday present), and I would be in a lot of legal trouble if they were not at least 18. And that was for a request in person ID, not advance with a statement I'd show them mine as well. Most passed on it, but one did agree and his ID showed he was just 19 and he understood that it was my concern he might not be legal (you have to be 18, or I get in trouble, civvie it's fine if you're 16+).
If it's an indie, they really shouldn't ask for in advance, maybe in person if you're borderline age. Agencies I don't know their standard practice.