I've noticed that as well and I think it's just due to the conversational feel of comment sections and forum threads. In person it would be a perfectly normal comment to make so it's easy to see how the impulse translates to online, but it's still funny to see.

Back in the early 2000s I would often link people to sites like justfuckinggoogleit.com or lmgtfy (let me Google that for you) which would perform the search for them with a condescending animation included. I like to think I've matured since then (I haven't but I like to think so)