Its not companies which reject but developers themselves
In other industries technologies change very slowly, what you learn today will be there for a longer time of period
When you have more an more experience on same most of the stuff will be trivial for you and you will be get paid very well
In IT technologies change much often, most of the technologies will be replaced within 10 or 15 years. So you need to keep learn in order perform
Your experience with those older technologies does matter for current projects, So companies would pay the same pay scale as for a one with less total number of experience. So ultimately you will switch careers
