Create multiple files for each file group for table partitioning?
One file per filegroup, one file per volume. 
So a partition read/write goes to one volume: which is one reason to partition.

Otherwise, you are simply using all 4 drives all the time. So why bother with partitioning

I personally don't like multiple files per filegroup (except tempdb of course).

I assume "4 drives" means 4 discrete SAN LUNs or RAID arrays...