Re: Ever train in everyday clothing?
It isn't a bad idea to think of a gi as a piece of training equipment, not a garment you are likely to wear in a self-defense situation.
A gi can even the playing field athletically. When training, a gi limits the advantage someone may have athletically over their opponent. The friction of two combatants grappling with gis is much greater than no gi. Due to the increase in friction it is much harder to muscle out of submission holds or bad positions and you are forced to rely on your technique much more.
A gi slows down a grappling match. This is another example of the gi being used as a training tool to help your technique. Not only does the gi limit one players strength/size advantage, it also considerably slows down the match. A slower match means more thinking, ad******g, and considering by both players. Slower matches allow you to make slight technical adjustments more easily increasing the technical level of the match.
Basically, it is easy to see the value of gi training if you think of the gi as a training tool that is used to increase your technical level of grappling. It doesn't necessarily best represent an MMA or street fight scenario, but neither does wearing 16oz sparring gloves, headgear, rashguards/whatever. It is piece of training equipment.