There are reasons we have a large intestine and it's ideal to keep your colon when your UC can be put into a solid and stable remission through medicinal means. Most try at least 2 biologic medications before going the surgery route. If you've tried everything and failed then surgery is an escape (about
25 percent of UC patients fail response to everything). Surgery provides control and predictablity and a good quailty of life to those whose UC cannot be otherwise be controlled.
Surgery isn't a first line treatment for uc due to inherent risk of an abdominal surgery, and not everyone has a picture perfect outcome with regard to bm frequency with a jpouch. There are sometimes complications like abscesses, pouchitis, decreased fertility risk, etc. Nothing insurmountable but certainly bothersome.
There are also some good blogs out there that really helped get a handle on what the process is like -