You do not need an oil cooler.
But there are a lot of things in this world you do not need that are nice to have.
Oil cooler will help reduce engine temps on hot days when riding.
It will not cool a lot. Many feel any little bit helps.
Good quialty true sny oil and lube plus a stage1 and an oil cooler works.
each helps a little the 3 all add up make a difference.
Stand by for a lot of reading there will be a few replys to this thread
Vist the Jagg site FAQ page good reading also and the self help section here.
IMO Smitty sums it up very well. There is a thread going now (HD
Turbulator) that has several comments about oil coolers. There are other threads about this but can recall there location off hand.