Other people have pointed this out, but I think you and others are missing the point. Sometimes simple (ie. boring) is a strength all on it's own. Mechanically, it's not as strong as some others. But there is a huge advantage to having an always-on ability you don't have to think about.
Two campaigns ago, we had a rogue in our group. You have no idea how long it took him to remember to use his bonus action hide-dash-disengage. He's playing a paladin in our current game, and he only smites if we remind him he can. Any kind of mastery ability (other than something like Flex) would be useless to him.
Most of us (especially here) are far more experienced at this game. But there definitely is a space for the casual player who doesn't care about mechanics. I'm sure we've all seen them...the players who are only there to hang out with their friends, or because their boyfriend/girlfriend are playing. And since those players are probably more likely than not to be martials, having a basic plus that works with a basic sword and board build is perfect for them.
Heck, I've got 40 years under my belt, and love cool combat mechanics as much as the next grognard. But there are times even I might not want to have to deal with an extra roll for every attack. Sometimes the thought that "Hey, I can get the benefit of using this two-handed AND still use a shield? All the time? Bonus!" is a good thing.