No it’s not. You would not tip any less if you knew there were other people at the restaurant who had no intention of tipping.
It’s strictly a lost potential income to the server when they land a cheap customer. It may not actually cost them anything at all if it’s not busy and they were able to take on the additional customer without losing a potentially higher paying customer slot.
Prices for basic services are lower in tipping cultures, ceteris paribus, since staff wages are a component of price, and staff wages are lower in a tipping culture since they make part of their income from tipping.
Hence, the cheap customer benefits to the maximum in a tipping culture since the prices they're paying are artificially lower as they've been subsidised by tippers. That's why it's a transfer of wealth from the generous to the cheap.
It's got little to do with whether the generous decide to tip more in the presence of the cheap (although that may be a small part of it), it's about the indirect and hidden subsidisation through service price.
Presumably it's a combination of both, where on a diverse platform like Uber it weighs more heavily towards socioeconomic drivers and in a more homogeneous environment like an expensive restaurant it comes down more to personality traits.
I still advocate tipping since it's a nice thing to do and probably improves your happiness, but I think it's healthier in the context of a no-tipping culture where wages are sufficient and baked into the price of the service.