Piano is different than guitar because (from my limited knowledge) guitar songs are mostly based on chords while on the piano the chords are often broken up into individual notes, eliminating the need to memorize/remember specific chords/scales.
A lot of guitar music, especially on the net, is written just as chords, which may be what you're thinking of. But the chords are the same notes whether you're playing them on guitar or piano. You could play exactly the same thing on piano as the guitar players do, and aside from sounding a little stiff, would make good musical sense. It's also common in pop and jazz for piano players to read off chord sheets (lead sheets).
Likewise, guitar music can be written out note-by-note just as piano music generally is. Classical guitar music is written this way, as well as rock leads.
Here's the thing about it, though. If you're thinking of it as individual notes, you're doing it the hard way. Scales and chords are a form of compression between the page and your brain, just as gzip is a form of compression between the web server and your browser. Once you figure them out, you can look at a measure and know what keys you need to hit without having to look at each note individually. Playing any instrument becomes much more fun once you have that skill.
On the other hand, if you're just playing "for fun," and aren't hitting any major technical frustration points, then whatever. Keep having fun. Just remember that if you start to not have fun, there are "icky" things like scales which can help you keep advancing. Scales can begin to help at any point in one's musical life.
My take is that you don't need scales to enjoy music. But you will also never be at the level of the greats.
I don't want to be a great pianist, I just want to be decent at expressing myself in musical form. For awhile, I thought this meant scales weren't really for me.
It turns out that, on the contrary, they are ideal for me because they quickly get me up to speed on what tends to sound good.
Ultimately, you're right, but scales may be worth a glance even if you're somewhere in the middle!
I'm still figuring out how precisely the circle of fifths is useful, someone feel free to chime in.