"Rustle everyone's jimmies?" Seriously? What does that even mean?! Are you British or Australian or something? "Rustle everyone's jimmies." Ha. What even are "jimmies?" Hahaha.
Okay... seriously. I don't know. I can't speak for anyone but myself. But psionics does "rustle my jimmies" (hahahaha). So, I can theorize, but in the end, it's just me guessing, I'm not even really sure why I hate psionics.
Thing is, psionics is kind of pseudo-sciency. It's a sci-fi thing. Really. Psychic powers are what you add to something sci-fi because adding magic feels silly. That's why Star Trek had mind melds and empathic betazoids rather than wizards and sorcerers. That's also why Star Wars had mystic powers and why people got mad when the Force got explained via midichlorions. Psionics and magic are basically the same thing, but one is fantasy and one is sci-fi. On a deep, subconscious level, that's just how it is. Now, some people are okay with sci-fi in their fantasy and I bet the same people who are okay with Barrier Peaks are perfectly fine with psionics in D&D.
On top of that, you've already got at least two different primary expressions of magic in D&D with numerous subdivisions (divine and arcane, paladins and clerics, warlocks and wizards and sorcerers and witches and eldritch knights and incarnates and on and on and on). Psionics is just one two many forms of magic, I think. Especially because divine and arcane magic are two sides of the same coin. They both work basically the same way, variations on a theme, with different sources. Which implies that's just how magic is. But then psionics comes along doing basically the same thing as magic, being magic, but being completely different from both perfectly good systems of magic that already exist.
And further, in some way, psionics has always been treated as a one off. Separate. Supplemental. In Basic D&D, it was barely mentioned. In 2E, 3E, 4E, and now 5E, it's not even a part of the core rules. It is always relegated to a supplement. Usually a supplement that gets resupplemented a couple of times during an editions run. So the system itself kind of treats it as a weird mutant outsider one-off. It's never really part of the core.
And further further, the rules for psionics are frequently clumsy, confusing, or just overly complicated. Again, it's just another form of magic. Why does it need it's own set of rules that are twice as complicated? It's a pain in the a$&.
So, thematically, psionics doesn't fit the fantasy ouvre. It's extraneous, it overlaps magic, it's overly complicated, and it's often tacked on. Some people love it, sure. But some people also love orange shag carpeting and Pacific Rim and spherical droids and dragonborn with tits. Find those people and slap them.