Unfortunatly, many hairstylists ARE taught to push professional products without really knowing how to formally discourage drug-store products, if it can be scientifically be done
The main difference in drug store and salon haircare is this: drug stores put their millions into advertising (think Christy Brinkly, Naomi Campell, Vouge Magazine and VH1), and salons put their millions into research (think of how many times you've seen an ad for Redken durring a Wheel of Fortune commercial), and then they rely on the salon professional to to the advertising.
Plain and simple. They do put some better ingredients in their products, thats why their spossed to be more concentrated and so you need to use less and they last longer. I have found many profesisonal products that I do not care for. Like medicine thats spossed to treat things from sleep disorders to depression, they all tell you that "they're not for everybody, consult your doctor". Sometimes it's just a trial and error for which products you prefer to use. Does it mess with haircoloring? Sure, to some extent. I tell people that if they find a drug store color they really like, then go ahead and use it if they don't want to come in and have it done, but dont do it if you like to change your color all the time as I would never recommend that someone use it OVER a salon color, just if they always plan to do it themselves. There is a BIG difference in salon and drug store color.
But back to the haircare, use what you like and what works for you.
HOWEVER, if you DO choose to go for a salon product, really price compare! And do it for real! Ive had many people tell me they'll get their product from the supermarket and it heats me up as the supermarkets in the northeast where I live have the same markup as the salons do! So you're not really always saving any money, and you have the ability to get help from your stylist and usually a guarentee that you're buying FRESH products and can often return them if they do not work for you...
Most stylists dont make hundread of thousands of dollars a year like everyone thinks they do and many salons make half their profit off retail which keeps them in business (and it isnt always much), so if you have a salon you really like then give them loyalty and do not purchase professional products from high end big business chains like Wal*Fart. Buy drug store brands from drug stores and professional brands from salons. Not to sound like im pushing this too far, but unless you're saving several dollars per salon brand products, is it really worth giving more of your hard-earned dollars to a big business that doesn't take care of their employees (and ill stop at that before I offend anyone

Also, supermarkets are known for "diversion", I don;t want to sound like one of those pushy hairstylists so ill touch on it only briefly: supermarkets and drug stores that sell salon products are "diverting" the product = selling it illegally. Warehouses have been shut down where they traffic these products. In instances they have been found to be old, outdated, comtaminated with more bacteria than normal due to aftermarket tampering, and in rarer cases, counterfit (sp?).
Afterall, they have to get these products without manufacturers knowing, so its a drueling process.
OK, now Ive vented. I try not to be a pushy hairstylist, but I believe in loyalty. If someone chooses to buy supermarket haircare, I dont diss them for it. But if they want salon products I educate them on what they get in a slaon products from a Walgreens, and then I ask them to compare the price and determine if their really saving any money from it.
oh, besides... did I mention that Pantene (P&G) testes on animales?