They get very, very hot, so their conversion efficiency falls sometimes as low as 12%. They also get dusty, which can cut conversion by as much as 80% again unless you dust frequently. And, getting so hot, their useful lifetime is reduced to as little as 20 years.
Float them on a reservoir instead, and conversion efficiency is improved to as much as 23%, lifetime increased to... nobody knows yet. Evaporation is reduced. Biofouling underneath is reduced. Some wildlife prefers the shade, under. Turtles like to climb up on the edge. And, cleaning is easy. (Search: "floatovoltaics")
Float them on a canal, likewise; the evaporation and biofouling reductions are extra important there. California estimates they could generate 12 GW on its canals, and prevent millions of gallons of evaporation loss every year.
Stand bifacial (double-sided) panels in fencerows on cropland, running north-south, far enough apart to drive a tractor and stuff between. They pick up morning and evening sun, while protecting crops from heat stress and cutting evaporation. Some crops yield more, few less. When you have plenty of crop land, you don't need them to pick up every last bit of sun; you have plenty of room, so they can be spread out. You could grow berries or cherry tomatoes under, whatever else you grow. They don't get so hot in fields, either, and the vertical mounting keeps dust off. And they produce revenue year-round. (Search: agrivoltaics)
They also do well in pasture, where the livestock keep the weeds down.
On some crops, you want them horizontal above the plants to protect from freak hailstorms, heavy downpour, and harsh noonday sun.
We all like parking under solar panels in parking lots, where they keep the rain off on our way to the car, and keep it from getting too hot inside. And, they make roofs last longer; not just on houses, but on warehouses, factories, airport terminals, malls, what have you.
Finally, deserts are usually a long way from where people want the power.
There is absolutely no shortage of places to put solar panels where they will work better and longer, and do other good besides.