The main problems are that like most property crime that isn't stolen diamonds or gangs of ludicrously attractive Americans executing complex plans to rob galleries and casinos, the police DGAF; and lack of secure parking, and by that I don't mean Sheffield stands. They'll argue it's hard to solve and there are other important things to focus on, but the reality is a lot of the time you could walk into a station with a complete profile of the thief, a video of the theft being undertaken, and a precise, current, accurate-to-within-2m GPS locator signal for the bike and get a muffled "we'll look into it when we get a chance" from the break room. Whether you'll get a conscientious and engaged officer of the law or a lazy feckless twerp stuffed into a uniform like a supermarket own-brand sausage is complete chance even for normal thefts, then with bike crime you also have to deal with the ingrained "it's only a toy innit, just use your car" attitude.
You can do all the bike marking and lock-advice-sessions you like, if the polis won't actually do anything beyond occasionally return bikes they stumble over when searching for entirely different illegal activity, and if the council won't build/appropriate space where we can have free *monitored* parking facilities at destinations, bikes are going to keep getting nicked and people are going to keep dropping out of cycling because of it.