I've played a lot of games over the years, both online and in real life. I've always appreciated the value of two players taking a subplot out of a normal session and playing it out, then incorporating it back into the larger group. I want to talk about why I do it, and why not everyone wants to do it.
The spotlight is the amount of time and attention a given player gets during a regular session of gaming. Ideally, spotlight is distributed equitably among everyone. I say "equitably" rather than "equally" because not everyone may want as much spotlight as other players in a given session. The important thing is that everyone feel satisfied, not that everyone get the same number of minutes.
Cutscenes can help solve spotlight issues, when they advance a subplot or side-story that would consume a lot of time at the table, and don't involve the entire group. For example, a key conversation or interaction between two PCs, or a PC and NPC, might take 30 - 60 minutes of real time to resolve. If the group doesn't want to sit through this, and if it doesn't serve the main plot everyone's involved with, maybe it's best not done during the session. But if it's important enough not to just drop or hand-wave, a cutscene can make it happen.
Cutscenes allow things to happen in a different medium or pace than a regular session. If the normal game is played by voice, there's an immediacy and propulsiveness to it, but perhaps a thoughtful conversation or meditative contemplation is better served by text, not voice.
If you are taking mechanical actions during such a cutscene (e.g. if two Masks PCs interact and there's a clear "Comfort and Support" fictional trigger, do you roll it?), some players feel that it's unfair, or a way to power-game. This depends on the system you're using, obviously, but it's more important for players to all feel comfortable with the game as a whole than to advance individual plot threads.
Cutscenes can reward players with the free time to create them, but conversely punish players who lack that time. Cutscenes should be used to solve spotlight issues, not create new ones.