There’s already hundreds of episodes in the Boruto anime. Yet, most of them don’t feature original bits of plot from the manga. Why does Boruto not follow the manga?
Boruto often does not follow the manga because the anime releases faster than the manga. The anime is releasing almost constantly, but the manga only comes out once a month. This means the anime must wait long periods of time for enough manga material to be built up for an arc.
Rather than animating a single manga canon episode a month, the show has opted to allow the manga-content to stack itself up as much as possible. This is done so that once the manga is finally adapted, it can run all the way through in a single shot without any filler.
Boruto’s attempts to follow the manga
So far, the Boruto anime has been able to adapt the entirety of the Kawaki arc. The monthly manga has since moved on to the Code arc. Another multiple year-or-so long drought of manga-focused content is to be expected for fans of the anime.
The Boruto anime prepares itself for upcoming manga arcs by writing filler arcs that loosely connect to the manga. For example, the anime-only Kara Actuation arc lays the groundwork for the Kara organization. Once a sizable amount of additional backstory adds to upcoming characters from the manga plot, the manga-centric episodes begins.
Filler or not, some Boruto anime-original arcs are worth watching for this reason. Naruto’s original author, Kishimoto, acts as a supervisor for the anime. That means that even if content doesn’t appear first in the original manga, any filler must still receive the greenlight from Naruto’s original creator.
Kishimoto also took over writing duties for the Boruto manga recently. This means that his vision for the Naruto universe is more clear than ever. There’s a bit more incentive to watch the fillers.
So that’s the answer. Boruto does not follow the manga because it comes out too fast. The Boruto anime comes out almost constantly while the manga only comes out once a month. The show waits multiple years for the manga to write an entire arc instead of adding in loose episodes here and there.