Why go oracle lens over normal wards?

Title! Ive reached emerald (not too impressive, i know) on jungle to preface, so this isn't a "I'm new to league" question. However, is there a reason oracle lens is picked 100% of the time in jungle?

I understand to spot wards to know if im coming, however, sometimes i can still gank after being spotted on a ward, or the other hand, if the ward is there and even if i do spot it with oracle lens, theyre gonna back off either way as they've already seen me.

Keeping wards (not that i do mind you) would allow me to perma ward the enemy jungle and track them constantly, would that not be more valuable? Or is it because its my job as jungler to clear wards/set up surprise brushes etc?

Im struggling to word my question/explanation properly I apologise, I just usually buy a control every couple backs to place in enemy jungle and i get so much value from it myself, i was wondering hmm should i start taking normal wards over oracle, but no one seems to do it