Why should I do a challenging job for the same money someone else does a menial job for?
Discussion
Because you're not a horrible and lazy human being?
Doesn't make sense to deliver a more valuable service at the same price as a less valuable one.
Pretty much the same reason anyone would. No menial job was available at the time. Pay people who aren’t working and they won’t work. Pay people the same for the easier job, there will be more workers for that job. The ones with the harder job will do it less well. And they should.