Because Google turned the computers into a commodity. These employees swap out broken machines for the most part, but the software stack is so redundant that you can pull out a machine running a key job and the scheduler will simply retry it somewhere else. Similarly for files with GFS. All machines have their own battery so the possibility of the whole thing going down is slim. It’s beautiful how they’ve evolved from running on Sun mainframes in the early part of the century. The workers at the datacenters basically do mindless labour, so aren’t paid like a typical sysadmin.
If they were struggling to find or retain talent or if they weren’t getting the caliber of employee required, they would certainly increase wages as they did with engineers.
When I was tangentially involved with a datacenter company several years ago, they had hundreds of qualified applicants for every job opening. It’s a job that a lot of people want but with few openings.
You would have to search a lot to find any big, international conglomerates with shareholders who would willingly pay higher wages for workers without a fight.
I assume some day they will want to use robots for this work. Amazon is already working on it for their warehouses. It is not much of a stretch to imagine they've had conversations about what physical work can be automated. I could be wrong.
They do? TFA says as many as half they techs are FTE.
The alternative is not that they hire everyone as FTE, its that they hire and fire FTE to meet their labor demand, and then we get lots of doom and gloom and stock price dips about Google firing techs in Iowa or wherever.