This also explains why Maverick let this game go on so long that he was late for his date with Kelly McGillis. He couldn't pass up the chance to make sports history. Plus, he knew Kelly would be really impressed with his record-breaking volleyball achievements, which might lead her to bend her rule against romantic relationships with pilots. Clearly, the strategy worked!
On a slightly more serious note, the producers of "Top Gun" used all sorts of clever camera angles and other tricks to hide the fact that Tom Cruise is much shorter than the actors in the other lead roles (including Kelly McGillis, who is several inches taller than him).