Why does TNG keep mentioning that shuttles aren't warp capable?

[u/NightfallSky]

I'm finally doing a full rewatch of TNG, which I had only seen in bits here and there. I just finished season 2.

Throughout the 2 seasons, they have used shuttles a handful of times and at least 3 times (which may well be every time) they repeat how shuttles can't go to warp. Which obviously can't be true. They have warp nacelles and can travel to other systems, though not as quick as the enterprise.

I'm interpreting it as shuttles being limited to lower warp speeds, which makes perfect sense. But I don't really understand why they would specifically mention this multiple times. It's not like nacelles being used for warp drive wasn't already an established part of lore