Because most of the routes have not been tested yet - all of them have been put together by volunteers during quarantine. And, from experience, even though they've been constructed from public footpaths, that's no guarantee of their quality. Paths can be fenced off by landowners, go through cattle fields or be outright missing.
Making all the routes available without at least a brief check could lead to less-experienced walkers getting lost or injured.
From experience they will and it’ll also be a foot deep in cow shit (I do a lot of walking in U.K.). That needs to be listed on the routes.
Common hazards and inconveniences such as flooding need to be listed. I had to Wade knee deep in slurry once where a river had flooded into a muck pile. I considered throwing my legs away with my shoes after that.
Cows yes, bulls no. There are exceptions but generally it's not legal to leave bulls alone without cows in fields that have public rights of way. We walk through fields with cows all the time, it can sometimes be uncomfortable if they come close but I've never felt in danger except when there was a bull. Two walkers have been killed by cows this year, although that's not typical.
Show us the draft routes in an interactive viewer, please. The page at the moment is a glorified mailing list sign-up box.