Because it would be an inefficient use of their capital given their other alternatives.

Also, if a small investment in the space can spur the incumbents to increase their own investment, the leverage Google gets from their own small investment is tremendous.

Because scaling would be phenomenally expensive.

To be exact, I am surprised they were able to make deal with cities where Fiber has launched given telecom franchise basically is a in-or-out. I guess they are Google they have plenty of resource at disposal.