The reason it will run so much better with the PC, is because the A/F will be closer to being correct - all the way across the entire map. Without the PC, or a good tune with ECU editor, Bazzazz, whatever - (choose your poison) the A/F is NOT right. For people who do not care how their bike runs - for people who do not care that their bike is not running its best - your are right, it is not totally needed.
Would it surprise you to know that a stock bike with a stock exhaust system and stock air cleaner can be mapped better than how it comes from the factory? I had a 2005 with over 20,000 miles on it in my shop last month. The customer wanted a powercommander, and he wanted it custom mapped. Guess what? When I targeted the proper A/F for a Busa, and went through all the throttle positions and rpms, I ended up with values in almost very single powercommander cell, indicating that the stock ECU map was not properly targeting the A/F across the board - again, this was a completely stock bike!
In fact, prior to the custom map, this stock, tired old Bus made 160 rwhp and 98 ft-lbs of torque SAE. After my custom tune, it made 168 rwhp, and 104 ft-lbs of torque SAE. It had better throttle response and more midrange, and more power everywhere - than before. The customer was thrilled, and after a good ride, told me I had given him back a completely different bike. One thing is for sure - a custom map from a reputable tuner is the best map you can get for your bike.
So. with all due respect, I guess everyone has to decide for themselves what is "necessary". I just know from experience that it ain't necessarily "right".