It's the texture.
The taste is distinct, but not really bad. I don't mind the mild flavor left over in a sandwich that had a tomato slice.
But I can't stand the texture of a tomato. Not sure exactly why, but even a small chunk in soup or salsa makes me gag. I blend salsa up so it's consistent.
And onions are both for me. A tiny piece of onion will ruin the entire burrito. From the weird crunch to the taste that lingers even after I down a few chips and half my drink.
I go through onion powder fairly quick though, I add a little bit to a lot of my dishes.
That's the point.
Set the bar low, but just high enough that tons of people still trip over it.
Sit back and enjoy the comment wars.
The people who are confident but wrong are too proud to admit they were wrong even if they realize it, and comment angrily.
The people who are right and know why, comment for corrections and some to show off how S-M-R-T they are.
The people who are wrong but willing to accept that just have their realization and probably don't think about it again. So do the people who don't know and/or care.
But those first two groups will keep the post going in both shares and comments, because "look at all these wrong people"
It's all designed to boost engagement.