Over here, you find the Nikon binoculars mostly in camera shops, with the posh ones also stocking Leica and Zeiss. And in these shops, Nikon has a very good name because of their cameras and sells well.
And Steiner is everywhere, of course. When I was trying out several binoculars in a very up market store some days before, I overheard this conversation between another bino-shopper and the sales stuff: "What do you sell most, Leica or Zeiss?" Answer: "Steiner". The latter to be found, together with Eschenbach, in most outdoor shops and with opticians.
As of which brand to carry or not, my experiences from a past life behind the counter of a specialized outdoor/mountaineering store are these:
General approachability is very high on the list, difficulties in communications cost time, energy and money. This is a make-or-break subject.
Getting the goods is important, if the they cant deliver, the shop cant sell.
You want as few suppliers as possible.
If everything equal, the brand with the most diversified sortiment wins.
Warranty and similar services, if the brand makes live easy for you, thats a definite plus.
One example: underwear made from merino wool is the big hit since several years. Very expensive, but sells like hot cakes. One particular brand, not the very very best quality of wool but very nearly a household name in this segment, has made any warranty claim a no-brainer.
The costumer complains about something, no matter what, even if he f####d up the garment.
The shops simply hands out a new garment, sends a mail to the company and gets reimbursed.
The "defect" item, mostly with a very small hole somewhere, will be officially put in the bin and effectively be worn by the staff. After all, they are still serviceable. Everyone is happy.