They have many teams making their own web services, so replacing AWS with in-house infra would require an AWS-like “private cloud” feature set, backed by geographically distributed datacenters. Network segmentation that is managed by configuration, user accounts with permissions to do specific things to specific services, etc. Engineers to build all this stuff are not cheap, and management to build and migrate to it cleanly it is not easy. If you can do this you ought to be selling cloud services. Even if it makes sense for Lyft to implement this, it would take a while. The RIO is probably much better on improving their core product, where there is more than $100M/year at stake.