Unfortunately, people do walk away from games, even in blitz. Maybe 30 seconds is a little short, but if there were no game abandonment rule, then the complaints would be about having to wait so long after a game was abandoned.
“Game Abandonment”

You have to realize that this policy may be, in effect, the lesser of two evils. On the one hand you have an unstable connection and sometimes your opponent has to wait 30 seconds, which I agree is not unreasonable even in 3 min. Blitz. But then on the other side, you have a LOT of rather immature players who just automatically hit the disconnect button the second they feel their game is threatened. In these cases, which are numerous, the 30-second time out rule makes a lot more sense. Otherwise many innocent players would have to wait 2 minutes or longer just because of some hot head player.
Allowed disconnect time and abandonment depends on the time control. If you are having major issues, you probably should play longer time control games.
https://support.chess.com/article/213-how-do-i-fix-my-disconnect-lag-issues
https://support.chess.com/article/338-how-does-game-abandonment-work