Yeah. It feels a bit like a bribe to give them something before they write the letter, too. Not uncommon once the letters are sent off, though (unless school rules prohibit it).
We did thank yous AFTER letters went out. Anything before that feels like a bribe. (And the thanks was a card and homemade brownies as I recall).
My younger son wrote a note to his GC (in addition to some small gift of cookies I think). He had gotten into some very reachy colleges and he told her he was sure she had helped with whatever she said. She was so touched she called me up to gush about what a wonderful son I had and no one had ever written a nice letter like that. So don’t just give them stuff, write a letter - it will mean a lot to overworked GCs.
Hmmm… I’d lean toward the “mommy lense” answer. I suspect the teachers are concentrating their efforts on college LOR and will do the same for your kid in a few years.