And, literally, smaller.

If you cut a book into lots of little events, you can slowly transport it over any medium because the file size is tiny.

Requiring high throughput to move data makes the data transfer easier to monitor because you're forced onto fewer channels. Typically, the Internet.

For a lot of data, speed is not important to the success of the transmission. You could click "download book" and go to bed and wake up the next morning to your downloaded book. The events would just trickle in, overnight.

Another thing is negentropy. Anything that you want censorship resistant will eventually end up on more relays, if the events remain small, as capping event size is an easy way to prevent spam or stymie the transmission of binary data (like kiddie porn).