Those who complain that it takes too long to do homework assignments are not being honest about the actual time it takes to prepare for the traditional trivia-based interviews where it takes weeks and sometimes months to prepare. Somehow it's hard to find 2 - 3 hours for a homework assignment, but 6 month to prepare for a quiz interview is totally ok. Exaggerating a bit to make a point ;-)
Technical interviewing shouldn't be a separate skill engineers have to master because nobody wins here. The companies get people who are good at interviewing instead of doing the actual work the companies care about. Of course, the communication part of the interview is important because the engineers will need to work in a team environment.