Technically you are supporting the corporation, BUT the sales numbers are counted for each store. So when corporate looks at the numbers, they can see "This store is doing lousy, replace some management, check for complaints, find out why.." and when they see good numbers(high sales, low mortality in live animals) they can support the store with promotions and find out what is working well there, and not working at the lousy stores.
So even if it's a corporate store, there's a lot of individuality to each store and even down to each section. The corporate folks can see "Birds have made a ton of sales" and "Reptiles has lost half it's inventory" and look into that, look into praises and complaints.
So if you want stores to improve, make your voice heard. And make sure you sound like a reasonable intelligent pet owner, not a psycho insisting that each 'scale-baby' needs a satin lined hide with evian waterfalls. Make sure you call on good stores in addition to bad.