Hello,
for most games, when bots aren't available, it means that it is either not technically doable, or that it wouldn't make sense. For instance, in the Little exam, how would a bot judge your answers? Never mind that, but how would a bot even give its own answers? A basic dictionary wouldn't be enough, since many categories rely on proper nouns. Simply put, this is a human, and a typical social game.
Something similar could be said about the Quiz, where a bot would just give random answers, though some kind of solo mode concept for that game wouldn't be that bad.
In games like Go/Chess/connect 4, technically speaking, the Playroom uses an engine to let the bot run on your own device, as it would otherwise be too resource intensive for the Playroom server. Such an engine doesn't run on the web, that being said, I'm optimistic this might be possible in the future, if not already worth investigating. For the developer: Someone recently put up an interesting technical discussion in that regard here.
For Scrabble, probably a similar concept would have to be imagined using an already existing engine, but so far, no suitable engine was found. Even if it doesn't look so promising at the moment, you never know what to expect. Chess was released many years ago, and the bots for it became available only recently, in 2021. By the way, in case you weren't aware, Scrabble is one of the games that you can play alone as well, if you want to practice.