Its all economics. Shimano has the quality and the price point for each level to dominate the cycling market. they are not catering only to small niche snob high end market that wants more variance,...they cater to all. It makes business sense to LBS to stock Shimano on their bikes. Will it change? Probably. I have a feeling though that it would take a long time for that to happen.
For every person that says Shimano lacks flavor or is boring or is not good enough or Campy is better.......there are ten that would vouch for its quality and reliability with the price to match. Thats what Shimano sees and that is what the LBS follows (most of them).
The key word here is "most". The product manager knows they cannot get all to like their product...they are targeting most. They are succeeding i reckon.
Ahhh the capitalist economy you have got to love it!