They provide some resilience, assuming their fallback usage includes multiple formats. Which isn’t a safe assumption, but even granting it, there are other prob

They provide some resilience, assuming their fallback usage includes multiple formats. Which isn’t a safe assumption, but even granting it, there are other problems with removing a codec. The most obvious being abruptly increasing the bandwidth requirements for all users of the removed codec. Even if that bandwidth is “free”, it can be significant enough to prevent access by end users with slow/spotty connections. Depending on the use case, that can have the consequence of also basically obsoleting the site serving those users. Just as some innovations enable whole new use cases, reverting the innovation can have the opposite effect.