Time - do it as a hobby so it's limited to people who are passionate about discovering something, not just trying to rack up points.
Access to human subjects - get people off the street. Universities can make access to student subjects easier but they're not representative of the world's people anyway so it's not that valuable.
Money to pay the human subjects - save up? People who're passionate about cars, for example, somehow find the money to build modified cars and don't need funding.
Ability - With the oversupply of researchers, maybe just leave it to those who can do it under their own steam? Hopefully undergrad degrees taught them enough to get started. This article says that university researchers aren't doing it with skill anyway but with luck or cheating.
Motivation - if nobody can be bothered investigating some effect, then maybe it's not really that interesting anyway and there's not much value in studying it?
What am I missing?