A base fee of 0 makes it easier for algorithms to reason about the costs, as the cost function is linear.
A fee rate of 1ppm is extremely low, and as such channels with a fee rate of 1ppm attract lots of routing attempts. However, based on my experience, such channels are quickly drained and rarely serve a benefit to the network. As such, they attract lots of routing attempts that will fail, which also makes it harder to find cheap channels that actually work at the configured fee rate.
Furthermore, an inexperienced node operator using the default fee rate for a new channel might not be able to increase the fee rate before the liquidity is routed at 1ppm. This happened to me more than once, and a higher default fee rate would have helped in these situations.