Well, you typically don't need anymore than 10 Watts to work a repeater and if you do, then it forces you to build an antenna that will increase your ERP. It teaches you ham radio and reinforces the principles. You start applying the math equations to design better antennas. Once that sinks in, it begins to make you a better, more knowledgeable ham. I'm a General and have been for a while. I see people all the time that go from nothing to Extra in a very short time and they constantly ask questions to which they should know the answer. When looking at a 6-inch quarter wave UHF NMO antenna they'll say, "Is that for 2-Meters?" Or, "Is that oil in those lines?" when pointing to RG-142 interconnection coax cables on a duplexer.
People have turned the amateur class steps into a contest and they think that just because they are an Extra, that they somehow, all of a sudden, know more than someone that has been doing radio for a long time. I watched a guy go into a testing session, take and fail the Extra test over and over until he passed. The VE team kept letting him pay every time. He just kept guessing until he got it. I don't know how many times he took that test, but it was at least 5. That's just wrong. It was wrong of the VE team to allow him to keep going and it was wrong on behalf of the test taker, because he knew he didn't know or understand the material. An Extra used to be someone that you went to for help. Now, I have Extras coming to me for the answers. They don't want assistance, they just want the answer. They don't care what process is used to get to the answer, they just want it given to them.
I'll close with some numbers. Say a Tech has a 5W HT and just can't seem to get into the repeater, so he finds the plans to build a Yagi that has 12dBd of forward gain. After coax loss of 2dBd, he magically has 50 Watts ERP. There are no arbitrary limits when you know how to overcome the problem with the power of knowledge.