Here is what I can think of
The pet owners: They want to see their animal grow, with many morphs becoming more and more affordable (<$1000) many people chose to have them as a pet and want to see their pet grow.
The breeders: For people looking into breeding the thought process when they see an adult is what is the problem with it.
Adult being available for sale make some people wonder, they wonder if there is something wrong with the snake, lazy male, female having issues etc, some those people don't realize that people who breed "upgrade" their collection as they go, letting go of proven breeders normal, single gene etc to replace them by multiple gene animals.