Ya' know for arguments sake I can sorta understand why they made us wait for the lovin' til' the night before the big battle in the first game because essentially these characters are new to each other and like with any relationship, things take time to build up....you have to get to know each other, the attraction grows over time, etc....
Plus considering the regulations against fraternization amongst military folks, it made sense that even though they were interested in each other, they'd put it off until the time was "right"...and regs be damned, the night before something like Ilos, after they'd already stolen the ship and were likely facing charges and were possibly going to die........ everything would come to a head and they might as well indulge in some physical gratification asap because who knows when or if they'll get another chance?...
And the second one is similiar if you choose to romance someone new...it takes time to build a relationship, even one that's essentially a friends with benefits thing...so it's understandable that there'd be a wait until the night before a "sucide" mission, at that point you'd likely want some comfort and wish to consumate your newfound relationship because there may not be another chance...
Perhaps if there are some new romantic possibilities in ME3, I could see putting the sexytime off for a bit until you've at least established something concrete.
But for those who have existing relationships, those who have stayed with their ME1 or ME2 LI's, I think it'd be really lovely to have the opportunity to be with them fairly early on...maybe even share your cabin, if you choose too...*sigh*...we'll see how things turn out, hopefully it'll be okay....
It's funny that there are some that think it's silly to concentrate on the romantic aspects of the game....to be sure it's a small part of the series, but it's one that means a lot to a lot of fans and really serves to immerse yourself in the game universe...it means more IMO to fight for the universe when you've got someone you love along side you....
Eh, I realize it's all subjective really....there are those that love and value the romantic aspects of the ME series and those who prefer to concentrate on the exploration/combat and aren't interested in developing relationships....I just hope that the devs will continue to deliver games that give us the chance experience the game in the way we find most entertaining...romantic/character driven or exploration/combat driven or even both...that's why Bioware RPG's are so damn fun and inspire so much passion in their fans (be it positive or negative), because they can be so many things to so many people...
sorry for the long ramble...it's one of those days