Earlier quoted context omitted.
> (For anyone who's ever tried to modify a reservation, the difference is astonishing. If you're booked with the hotel, all kinds of adjustments are at least possible. If you're booked with Booking, Travelocity, Expedia, etc., it's somewhere between hard and hopeless.) That's utterly backwards IME. On Booking.com, most modifications are the push of a button (that, crucially, is right there in the UI that I already kn…
I think you're talking about common modifications that the booking website understands how to make via the hotel's API. The GP, meanwhile, is talking about completely arbitrary stuff that is not part of any booking services's data schema for "modifiable properties of a booking"—and also, where the hotel likely doesn't actually have an API, because it's just some family-run thing, and the booking website is maybe just…
Being able to write a message and have them get back to me (even if all they're doing behind the scenes is calling the hotel) is a much better UX than having to make a phone call during business hours, particularly when there's a language barrier.
> If you book through a booking website, and then you speak to the hotel, they will tell you that they can't help you, because they want to charge you more, but they don't have the ability to charge you anything, since they're not billing you; they're billing the booking agency. And the booking agency itself has no way for a hotel to add an SKU for this kind of customization. (If it did, it'd be abused by unscrupulous hotels.) They'll then tell you that they can fix your problem if they cancel your agency booking and then re-book it through the hotel itself... but in so doing, you might not be able to keep your reservation.
> If you book through the hotel, you can just speak with the hotel, and enter into whatever private direct customer-to-business deals you like with them to negotiate whatever kind of special service you want from them.
Meh, that seems like a bullshit excuse to me. If they're selling me some special add-on service, surely they can bill me for it independently of my booking. If I'm already going to the trouble of calling them (ugh), having to give my credit card details separately is not making that a whole lot worse.