Money is the main driver, of course. I think this trend started in the UK.<p>Before the EPL, most English soccer clubs had one home, one away strip. It wasn’t that long ago that the only writing would be a single number on the back, a club crest over the front left chest (“near the heart”, you see).<p>Around the 1980s, it seems to me that European leagues started to experiment - England taking a bit of a lead - with shirt sponsorship. One side effect was that shirts suddenly aged. Show me an Everton shirt with “NEC” on the front, or a Manchester City shirt with “brother”, well, I know roughly what season that shirt is from.<p>And fans want to wear the current shirt, often. We can take the piss out of the “full kit wanker”, who turns up to a game in shirt, kit shorts and socks, waiting to be subbed in to his favourite team, but people like to show allegiance and they like to show they’re up to date - in the UK even your car number plate tells your neighbours how “with it”, and therefore how rich you are.<p>Each season a club changed its shirt it would see a boost in income as new shirts would replace the old. This was new. And it gave them ideas.<p>First, what about changing the kit when the sponsor doesn’t change? Some graphic design element, a neck line, maybe a subtle colour change?<p>Then the “third kit” came in. Often used in cup competitions, but occasionally an option for league games. Infamously one grey third kit had to get changed at half time at Old Trafford, as none of the Man Utd team could see each other.<p>And then as some non-domestic leagues took more prominence - European football in particular - some clubs decided to create home and away kits for those competitions specifically.<p>So now we have a situation where clubs like Man City have 3 “base” shirts, plus goalkeeper, plus fashion variants, plus the women’s team…<p>If other leagues can get away with this, they will. Most European leagues have a similar thing going on, and it surprised me that NBA took so long to catch up, and that NFL haven’t gone at this at full throttle.<p>And of course, it has created a collector’s secondary market, special editions, anniversary shirts, “retro editions”, and so on.<p>Sports teams sure know how to milk passion via the wallet.