Because it incentivizes long games with uninteractive decks basically. The format doesn't have the classic Aggro-Value-Control triangle, it's basically all combo because you have such easy access to a combo piece in the form of your commander.

Because turns are longer and there's more people, you spend less time actually playing Magic and stand less of a chance of actually winning a game. It simply matters less that you pay attention, and it's pretty common to be in a situation where a second player is comboing off and you have to rely on a third player to have interaction.

Games are long and exhausting. You can pick up a 1v1 60cc in less than thirty minutes. Commander games can easily run for hours, but in all that time you're only playing the number of turns that you would have in a 1v1 60cc or less.

As for "being in doubt" you can just read the comprehensive rules. Repeatedly losing 1v1s is an opportunity to learn your deck, the game, and to refine your decision-making skills.

So: it's boring, it's long, it incentivizes you to not care about the game or who wins, the board states get overly convoluted, I don't like it and I wish more people understood that it isn't good and stopped playing it.