Industry wants to have the best memory, SATA, PCIe controllers, floating point units, SRAM units, etc.

Those components need to be optimized to the particular process and the companies that are best at developing them are also the same companies making the tools used to design semiconductors in the first place.

Cadence has to build a feature to design analog electronics in their software package. Then they have to make sure that their designs are compatible/manufacturable at all the foundries. This means they will inevitably develop all the basic components anyway and there is not much point to avoid paying them for the end result.

An integer adder or a multiplier is a commodity, the same adder optimized for a specific fab is a specialized good worth tens of thousands, if it means you can avoid the hassle of a tape out just to test your novel design. Nobody is realistically competing on adder designs and for the complex analog stuff, the development effort may add up to several tapeouts.