This is a common question in many sports.
A sponsorship is what Thorpie has from Telstra, kind of here's the cash now put the logo on your head sort of deal.
When a kindly retailer or wholesaler offers to support you it is more of a contra deal. This can be discounts, freebies or good trade in prices. The people that receive these are big consumers with lots of dedication and enthusiasm, and not necessarily the 'best' rider. The benefit for the shop is that the rider is loyal to the shop/brand, talks the shop/brand up, has a good knowledge of the product and is always happy to chat about their favourite toys.
So if you provide around $4000 turnover to a shop/brand every year you too might find yourself on 'the team' with free watches, sunglasses, towels, T-Shirts, early release gear etc, etc.
If your riding around on last seasons gear and not a big consumer you just don't rate.

That is the law of the commercial jungle
How much for the doggie ?