I wonder why Pentair cares. What's in it for them? Financially speaking, you'd think they'd be more interested in moving volume than in preserving the ability of some middle man to skim a little off the top of the transaction. There's some financial benefit that isn't apparent. No rational business will intentionally take action to reduce their profit.
Rebates for in-store purchases help Pentair's brick & mortar distributors compete with the online sellers. Pentair cares because the brick & mortars are essentially showrooms where people go to kick tires and ask questions about Pentair products. It's to Pentair's advantage to keep them in business. The rebate effectively compensates local stores for the flooring and other expenses they incur. It prevents the price cutting online sellers from getting a free ride on the efforts of local distributors.