I'll agree that "everyone" is probably an unfair characterization. But the tax benefits of depreciation are wildly touted among real estate investors.

If they didn't claim depreciation in prior years they can still get it via Form 3115. Yes this is complicated/annoying to do (almost certainly need a CPA), which you can argue is unfair, but I'm still going to have limited sympathy for anyone DIYing in this space without talking to a professional.