I suppose when you think about it the real celebs aren't papped much; i.e. Streep, Depp, Mirren etc. They get photographed at events and such but you rarely see anything of them leaving restaurants, grocery shopping etc.
Yes, it's 99% work-related. Premieres, film fests, award shows, and apart from the odd candid here and there, nothing. eg. Meryl Streep cycles around her town all the time and no one bothers her.
It's possible to do it, and I do think, for the most part, much of it down to the celeb themselves. They set the tone. If you think of most of the (proper) A-B listers here in the UK, you never set eyes on them unless they're promoting their work or involved with some event. And not an entourage or security in sight, usually only their press agent to deal with requests/answer questions.
The ones who say they can't walk down the street without press intrusion are usually the ones who can't live without it. And have the biggest entourages and the meanest looking security just so you know how important they are.