Why does Instagram count time in weeks? Why not years

Instagram's post timestamp goes seconds, minutes, hours, days, weeks, and that's it. It always says weeks regardless of how much time has passed. Weeks is the maximum time increment for Instagram. So if something was posted 4 months ago it says "16w" which is more normal in my opinion for it to count in weeks until one year, but if 2 years have passed, instead of "2y" it says "104w," and even if a post is somehow 100 years old, it will say "5217w." Why not just use years to make it easier to calculate for average people? Seriously, nobody wants to calculate how long ago "121 weeks ago" was.