Might be revealing a profound misunderstanding, but isn't that just because of the reference point? If UTC+0 were the The Chatham Islands, then a few would.
Yeah that isn't covered by what I said. I wonder if it relates to convenience. Having the same time as your neighbour is probably more handy than having a day that is off by 15 in my opinion, even off by 30 wouldn't bother me much. There must be countries that have muddled through this scenario. But it still leaves a question as to why only certain time points are chosen and others avoided.
It has been pointed out that there are many, but no one has explicitly mentioned Newfoundland (UTC−03:30). That has always been the most familiar to me as when I was growing up, television programs would always be advertised with a time such as "9:00pm (9:30 in Newfoundland)."