This mostly relates to stuff you disagree with (politically, etc):

It’s really easy on the Internet to live in a bubble, surrounded by others and material you like and agree with. This is especially true when it comes to the political right or left. Posting/viewing material from the “other side” serves three purposes: 1) it’s different from what your Internet crowd posts and therefore novel and interesting, 2) it’s something to gawk at, and 3) it keeps your crowd up to date on what the opposition is doing and thinking, which is important if you want to debate/defeat/win them over.

Example: you’re on the left and a “look what the right is memeing” sub/community starts posting a lot of trad-wife material. You have now been 1) introduced to a new concept (and thereby upgraded your Internet cred with new slang), 2) provided with novel material to yourselves meme about and make fun of (in this example, Ben Shapiro’s sister’s oversized titties), and 3) inoculated to the concept so when your 19-year-old cousin starts whining at Thanksgiving about how all the women at college are sluts and why can’t he find himself a good traditional wife you can give his manosphere-brainwashed ass a thorough smackdown thanks to some sweet rhetoric you picked up from the snarky comments section of aforementioned posts, instead of weakly stammering something about equal partnerships (or worse yet, not understanding the nuance behind wanting a “traditional wife” and thinking this is a perfectly normal expectation for dating in the 21st century that totally won’t lead down the path of inceldom).

There is another, 4th reason: self-reflection. Sometimes, during a blue super-moon lunar eclipse, you see content that’s from the other side that makes you wonder, “are we the baddies?” Or perhaps, “okay maybe they have a point there.” Or at the very least, “yeah I can see where maybe we’re not at our absolute best on this particular aspect of this specific issue.” At least, it would be nice if that ever happened, right?