I think the insistence on halal is a territorial thing too, its an assertion of Islam in the public space. It also creates problems. There was a case a few years ago of Muslims in a school in Kent demanding halal meat be served at school. Well it turns out that they just made all the meat halal, and other students didn't realise this, for a while. It turns out that Sikh students had been eating halal meat, which they are not allowed to do, because they don't believe in ritual slaughter, and other kuffars in the school objected as well. So the halal imposition can actually create problems for others.
Wow sounds like a school I know of, but not in Kent. My Muslim mate goes there. A new headmaster had replaced the old one and it turned out he was a convert to Islam and made sure nothing but halaal food was served at lunch time. I heard the students there were complaining too. I think they started serving non-halaal food again.