It's the same release model as Chrome. Chrome doesn't go from 10.1 to 10.2 to 10.3... It's a time boxed release. 4-6 times a year you get an automatic upgrade and the version number is increased. They could have chosen the smaller increment like 10.01, 10.02, ... but then we would never have a major upgrade, and I think humans prefer the major upgrades numbers. In reality, it's just a number. They could have started with 3.14 and added the numbers of Pi, but that's already been done.

I wish the lesson learned from Chrome was that version numbers don't matter. I think it's unfortunate that some people have drawn the exact opposite conclusion.

Marketing reasons, tech blogs don't write about minor version increments.

They're going to make four releases a year, so there will never be another major release. Sticking with the old numbering scheme would result in "deflated" version numbers like 4.39.

Because every release of Firefox could potentially break APIs.