Some people (like Rees Mogg, Redwood and some of their billionaire tax exile cronies) want no deal because it would be a great opportunity for "disaster capitalists" who could swoop down like vultures to buy up the assets of all the British businesses which go bust, making a fast buck.
Some people want no deal because they have believed all the lies of the Leave campaign and the right wing gutter press that brexit means "we can spend £350m a week more on the NHS, "we can have cake and eat it" because "they need us more than we need them", "we are a global trading nation and the rest of the world is desperate to do deals with us" and all the rest of the unicorns, rainbows and sunlit uplands.
Some people want a no deal brexit because they live in miserable forgotten communities and have been fed the lie that it is the EU, not successive UK governments that are to blame. They just jumped at the chance to kick that arrogant David Cameron where it hurt.
Some people want a no deal brexit because they think no-deal means we don't hand over money to the EU and can get rid of foreigners (especially the ones who came here to steal our jobs and our benefits), but otherwise everything will still be the same - no problems with customs, transport, import, export, just-in-time deliveries or the Irish border (these threats are just fake news)
Some people are so ignorant that they think that no-deal means we remain in the EU.