Why? If online products are cheaper, why wouldn't you buy online? Most people don't go into the store to check stuff out then go home and purchase online... If the store is price competitive and they're already there, they'll purchase.
We did exactly what you said this weekend. My girlfriend is getting super into skiing since I have been taking her up with me so much this winter. We were in Mammoth last weekend, and she decided it's time she buys gear and stops renting. At a local shop in Mammoth, she paid $650 for a pair of boots and was going to get the skiis there too. Turns out the exact same, new pair of boots costs $500 on Evo. We returned the boots next morning and ordered online.
The sales people were super helpful and knowledgeable, but it's not our job to make sure they stay afloat. Brick and mortar stores need a business model that does that for them.