You're right - a quarter isn't a reason to skip the maintenance. But for the same reason that CA is requiring that all gas stations provide it - call it the principle of the thing - I think it would be nice to at least know who's offering what, even if it's not required of the merchants to provide.
For that matter, the websites that list gas prices can tell me where to save 1 or 2 cents per gallon, which can often work out to the same two bits per stop. And in my area (mid-Atlantic), good luck finding air service for a quarter! 75 cents is more the norm.
So why the listings for gas and not for air? I'm just curious. I suppose more people stop at gas stations for gas than for air (more demand = more effort put into it), but surely I'm not the only one who likes to know where to go when the need arises, yes?