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.
The expanding-decimal notation is very appropriate for TeX, because its implementation is just converging to the behavior specified in the TeXbook (i.e., pi), not adding features.
