I personally love the HW 35's finger grooves, too. Very practical and such a time-honored, classically "German" detail. But it adds some incremental cost to cut them, and some folks just don't dig the look I guess.
Back in pre-Beeman days, the HW 30 and HW 50 had finger groove stocks, too. But the Doc didn't like it - his "R" woodwork for those guns killed the grooves and they've never returned.
Diana's classic line of sporter rifles also lost their grooves as part of an early-60's re-design.
Random thought, why doesn't HW do both? Maybe keep grooves on the standard beech stock for the hunters, and do the checkered walnut for the target shooters and collectors. Or find some other options; for years the HW 35 was offered with as many as four different stock designs at once after all.