Have you lost a client because you said no to cash payment?

I have never lost a client this way because the subject has never come up. We are not supposed to accept cash payments, this breaks Rover's TOS and subjects you to termination from the website. If you lose a client because they wanted to pay in cash, then it's probably for the best. They might not be trustworthy and may cause other problems during the stay.

Nope. I've had multiple customers ask if they should/can just pay in cash. Most have offered as a favor to me because they know that using Rover reduces how much I get paid. I usually just say something like "oh there's no need (to pay cash). Rover is great because I love the site and they give you insurance and 24/7 support when you pay through the site." They always understand or take the hint. If they ask again (I don't think that's ever happened for me), I just say that I prefer going through the site.

I always accept tips though, but I don't mention that to customers (I don't want to make them feel obligated to tip or make them to think I'm dropping a hint).

I agree with previous responses and add that I tell prospective, new, & repeat clients I honestly don't mind that the site's fees for business, customer support, administration, marketing and reemphasize that we would not have met otherwise (which they agree to and see the justification).