Does an easier life make people lazier?
It might not make them lazy, but prehaps less persistent and productive. The more obstacles you have faced and overcome, the easier your viewpoint on life becomes.
So maybe how much we achieve is more of a function of persistence in the face of difficulty. Persistence is a muscle you can grow over time: it is a focus to see something through to its completion and can be strengthened through exercising self-control.
Choose the difficult path over the easy if you wish to grow rather than stagnate.