Limiting relocation will not solve anything but just add salt to an already grown problem.

As already mentioned above plots have different values. I might snagged one in Goblets - my least favorite ward. Then something opens up in Lavender Beds - and now I have to make a decision: Do I go for the Lavender Beds and wait the three months before relocating again? Or do I stick to my hateful Goblets because I actually want to move to Mists but nothing had opened so far?

Plot-hopping is basically people trying to improve the value of their plot. Mostly they have a specific plot in mind (sometimes very specific with: "Mists, Plot 5!" - sometimes more like: "Shirogane, beach"). And you are losing lots of money on it because relocation is not free. You still have to pay a fee. Heck, when I wanted to move from my mansion back to a medium one I still had to pay a fee for relocation. So not only did I lose on the 50m I already payed for the mansion but also pay a percentage of the medium plot as well.

Plot hopping is a luxury not everyone can afford.