1) sponsorship exists to help sponsors sell products/services. It would make sense, then, for them to display options that anglers can afford. If all the pros fished NRX, Megabass, Tournament Extreme, etc, they'd be marketing a product way above what most of us can afford. The goal is for the prospect/angler see pros catching fish with the equipment and then immediately going out and purchasing it under the idea that "If it's good enough for Ike/Skeet/Clunn it's good enough for me." As opposed to "Ike/Skeet/Clunn are catching fish because they have a dozen $500+ Rods sitting on the deck of their boat."
Also, related, sponsorship is a huge part of how guys get paid. If you look at "career earnings", something like 2 million dollars may seem like a lot, but if you break it down over 20 years, that's 100k/year. Now, take into account travel costs, vehicle repairs, food on the road, tolls, etc and make adjustments for the expenses, the pro "making" $100,000/year may only be really making 50k before taxes. That really isn't a whole lot of money for a "professional" to be making in most fields. Money is made via sponsors, seminars, guiding, etc on top of whatever career winnings show, and have to make up a huge portion of earned income.
2) Despite the urging of the tackle monkey, we don't really need a locker full of $300+ rods to catch fish. The Rod is simply a piece of a tool (other pieces being everything else attached to it). The line, lure, and presentation are more likely to affect the fish's decision to bite or not. Also, none of this matters if you can't find the fish. Yes, better rods can help us cast them farther, feel them better, and get less tired/sore in the process, but it's not as essential in getting more bites as everything else.
3) Rods now are really, really good. For $90-150 you can get rods that are leaps better than anything available 20+ years ago. Just look at the graphite, itself. How many rods can you get with 30 ton or better graphite for under $200? How many different options that give you the grip/blank exposure that feels best to you? How many manufacturers make lines of rods with a huge variety or weights and actions for every presentation imaginable? If you need to tighten a bolt, you can do it better with a properly fitting crescent wrench than with a pair of vice grips that may cost twice as much, right? Though the vice grips may work, why use them is you're getting properly fitting tools for free that do the job perfectly without stripping the nut/bolt? - Especially if part of your job is to help sell crescent wrenches.