We don't concentrate light in the normal PV systems because mirrors aren't cheaper enough when compared to the panels. Things used to be different, then PV got cheap.
Solar water heaters are also much more expensive than they first seem. Houses with pools usually have them, but if you don't own a pool it's normally better to put your money in a more flexible PV.
It's mostly maintenance. Best concentrating mirror systems are Fresnel reflectors and they need meticulous cleaning, then there's a problem with heat dissipation for PV solar.
I understand it's now cheaper to heat water with a heat pump (or even a resistive heater) driven by PV, rather than by directly absorbing sunlight as heat.
When I run the numbers that's what I get. Also I think the Passive House nutters are starting to freak out because solar panels + heat pumps cost less than the extra insulation required by passive house regulations. Especially true because insulation quickly runs into diminishing returns.
How much insulation determine Passive House needs versus air-tightness? Isn't the latter also a metric that needs to be hit to get PH certification? Which of the two should be focused on (either by individuals doing a reno, or legislators updating code)?
Solar water heaters are also much more expensive than they first seem. Houses with pools usually have them, but if you don't own a pool it's normally better to put your money in a more flexible PV.