It’s actually really useful for web devs to have access to a local model. Whether or not browsers should bundle their own rather than using the system-provided model(s) is up for debate, however. For the time being, though, Google does have some of the better small ones.
Furthermore, users aren’t going to want to have to wait for an extra thing to download before their web apps can use AI.
That’s the thing… Without context of why, users probably wouldn’t want a 4 GB download. But they do want their web apps to work properly. When there’s a specific use case they’re interested in, they will want to have it, and they won’t want to wait.