.@theresa_may says 70 "technical notices" for businesses and households will be published in Aug and Sept setting out how we can all prepare for a no-deal Brexit (should that be what happens). Yikes
— Robert Peston (@Peston) July 18, 2018
"No deal" doesn't just mean oh, well, things get a bit messier. It means that the UK's relationship with the outside world basically...ceases to operate. It affects everything. I could spend all day providing examples. How about "UK airlines can't land their planes in the EU." That one not good enough? OK, how about "UK airlines can't land their planes in the US...or basically anywhere." Divorcing the EU doesn't just impact the UK's agreements with the remaining EU countries, it impacts their agreements with the rest of the world, as most of those are done...through their membership with the EU.
Some of these things could be resolved before the deadline, of course, even if there's "no deal," but the rest of the world has better things to do than worry about the UK's interests. I am sure US airline lobbyists, for example, will be quite happy to keep British Air out. The point is that's just one example... It's everything.