Dear Jayw77,
Dental bridges require the shaving of adjacent teeth. Dentists might be reluctant to shave healthy teeth as their main job is saving teeth, not impacting them. Also, because a better option is available, which are implants. Implants mimic the natural teeth and, unlike bridges, prevent bone loss. With a bridge you run the risk of it "floating" after a few years as with time your bone and gum will start to "shrink", meaning it will not appear as it is attached to the gum.
I am unaware of your health reasons are for not choosing implants, but keep in mind there are different type of implants for different type of patients.
I hope to have answered your questions.
Kind regards!