right - in simple terms, because it doesn't matter enough to them.
All aspects of our society are political to some extent. Of those, different people will have different orders of importance for each issue. Some while very important to me/others, are issues generally all major parties are agreed on (like say, democracy, woman having the vote, the rule of law), so aren't decision making issues between the parties. Everything that's not exactly agreed on between parties will have different 'weight' of importance to each voter, effectively putting them in order and the top ones will be what people decide on.
If you recieve or know someone who receives disability benefits, then that issue will be pretty high up your political issue priority list, for those who don't, it is unlikely to be the key issue.
You said how does anyone think it's ok - it's 'ok' because something else or (more likely) several other things are more important when deciding who should be running the country and deciding over all the political issues.
I bet many people on here who have been effected by the cuts have a pile of issues they don't give a rats arse about, although the decisions taken by the government in those areas could have massive ramifications for other people's lives, but as you aren't effected or don't know anyone effected, it's not all that high up your list of reasons to pick one party over another - or even if you do care about it, it's not something you care enough about to be the deciding factor in who to vote for - great if your chosen party also mirrors your views on it, but won't swing you the other way.