Being an Irvine resident, I would say that the construction of new apartments are not at all about wasting money. Rents and property values here in Irvine are sky high, and demand is only increasing. Irvine is becoming Orange County's tech hub, is known as one of the safest cities in the US, and has the highest ranked public schools in the country.
If you are seeing a lot of empty units, it is not because they are building more units than are needed. It is more likely because a lot of them are rented by very rich tenants than only spend a few weeks each year in those apartments.