Switching APIs isn't seamless. Switching to a federated backend is even more of a hurdle. None of the backends are likely able to support the load that Apollo

Switching APIs isn't seamless. Switching to a federated backend is even more of a hurdle. None of the backends are likely able to support the load that Apollo (and RIF) would do (see also what HN did to Lemmy the other day). Many of the users of Apollo and RIF are using them and the APIs that reddit was providing for free before to avoid paying for things and seeing ads making monetization of those and supporting the backends even more difficult (not that Lemmy and friends want to pay for server costs with advertisements - they'd rather donations - but that isn't a reliable income stream).