I'm not sure how big of a factor it is, but scylla and red-panda are both source available, and VC funded, while the projects they are trying to replace are fully open source, and owned by a non-profit foundation. That probably isn't the only reason they are struggling, but it is a potential reason not to switch.

Granted, scylla used to be open source. And turso is VC funded and potentially vulnerable to a license change in the future.