I got the Pentax smc DA★ 200mm f/2.8 ED (IF) SDM from an online camera gear rental company as part of the Photography Stack Exchange Lending Library experiment. (Thanks, Stack Exchange!) This is a relatively fancy lens; one of Pentax's most expensive, and it's got heavy-duty build and features, including weather sealing. I wasn't surprised to see that the rental company sent it with a UV filter (which the insert says is "mostly for protection"), but I was disappointed to see that it's the cheapest Tiffen protection filter, which is generally not well-regarded.
Now, I realize that it's my responsibility to protect the lens, but part of my reason for renting is to see what the lens can do, and having it impaired by a cheap filter is not really what I wanted. So, I've taken it off and am going to be ultra-careful. Since I'm beyond phase where I had a high risk of a two-year-old suddenly flinging sand at me at the playground, I usually don't use a protective filter on my own lenses, even the pricier ones, and nothing horrible has happened to me yet. And this one comes with a really hefty and solid lens hood which makes me feel pretty safe in the field.
If the filter were a super-multicoated B+W or Hoya — or maybe even a fancier Tiffen filter — I'd be inclined to leave it on (at least outside of some technical tests). Or if I had a high-quality 77mm ⌀ UV filter of my own, maybe I'd swap that in — but I don't.
I'm going to ask the company about this, but I wonder if it's standard practice, and what people who rent lenses usually do. The company didn't even send a protective storage case for the filter; it seems pretty clear that they expect it to be left in place.
Do most camera lens rental companies send their lenses with protective filters? What kind of filters do they use if so? And what do people who do this a lot do about it?