Upvoted you to help with the downvotes you got for asking a question.
I had this opinion too, before visiting the bay area for an interview in 2011. I was stunned at how every single person (or so it seemed) had a mac out on the caltrain. And to answer your question, two out of the three companies I've worked at have been almost all macs (some devs like linux/windows laptops).
Not sure where you're getting this idea, but maybe your view is being shaped based on what industry you're in?
Everywhere I've worked in the SF Bay Area and the valley (tech companies) are 100% Apple shops for at minimum their tech employees. Many of them are all Apple for sales / sales eng as well as execs (airs, usually).
Some of the big ones are all-laptops (MBPs for tech, Airs or standard macbooks for other functions) with desks that have 1-3 4k monitors plugged in when working at the desk. Other companies had a ton of trash cans deployed at desks in addition to the MBPs.
I have less work experience on the east coast, but in major east coast city offices I've seen similar.
Less common is an understatement. In Europe, where software development has always been a cost centre and margins are always thin, Macs have been downright rare until the late 2000s. They were “the computer for people who don’t want to know about computers”, with a very small and dedicated niche of developers that never intersected with the enterprise world.
haven't seen an engineering shop in a while that didn't offer macbooks to engineers. At least 8 years. Internally at Google for instance almost everyone is on a macbook.