Harry knows a lot of boys who do it because they need the roof over their head, or because they think they owe Harry. He knows he can come across as a man who gets what he wants - he is that kind of man - but he doesn't want to impose on any kid. Consent is important to him, at least when it concerns his own sexual encounters and affairs.

As soon as he has it, he leaves Neil's trousers to get the kid's shirt off first, if only because he kinda likes how he's sitting on his lap right now and taking off his trousers requires Neil to move.