"Experience" doesnt equate to "time served (or seniority)" with a particular employer! Relevant experience may be gained from another employer and so will the use of "experince" in place of "seniority" only open another can of worms?
If someone has had 10 years "experience" in a relevant part of the industry and an employer is paying increments dependent on "experience" then he will be able to join the company with serveral years of increments!
This is the situation in teaching - A newly qualified teacher is more attractive to a school as they are on the lowest pay scale. A teacher with many years service will have to be paid the salary scale comensurate with there "experience in teaching" and not time served with the school. The net result is the dilution of experience as companies recruit the lowest common denomintor and the more experience you have the less attractive you are to a new employer!