Probably the volume of users in the free tier is too big so they need to reduce expenses. It might be like giving away free storage space, too. There may be 0.0

Probably the volume of users in the free tier is too big so they need to reduce expenses. It might be like giving away free storage space, too. There may be 0.001% of users that have a crazy amount of usage compared to average. At least my OSS project got to have many free builds, props to Travis CI.