My understanding is that most of the high performance funding isn't necessarily for equipment - it's for high-end trainging: sports psychologists; fancy dieticians; fancy sessions with video analysis etc. The stuff that makes a tiny but important difference at the international level. Well-funded field sports probably have access to this already, but smaller national sports don't.
+1 I believe this is where a lot of the Tennis funding goes. Part of the problem with that sport, as with golf, is the clubs being relatively exclusive though. There aren't good enough public tennis facilities around for kids of the lower socio-economic groups to use and to be honest, it's poorer kids who are probably more likely to dedicate their lives to getting good at a sport if they're talented. They don't have as many other options or family pressure to go into a more solid career as middle-class/ wealthier kids who might be less focussed. If they're well-heeled, middle-class kids, you might spend a load of money on them when they're juniors but, even if they're really talented, they might drop out of the sport as young adults for these reasons.
Also, while you can divide a tennis court into two or three mini-courts for the small children who are just starting out, when they get to play tennis proper it's only two to a court for singles which is a lot of space and time to dedicate to only a small number of players and when most of the court space is in clubs, the kids have to get out of the way for the paying adult members who want to use them for recreation. Bigger field sports are more economical in that way - you can pack more kids on to them at a time.