Maybe because Intel "desktop" processors are just laptop processors in slightly different packaging. Or maybe they want to push more customers into the more expensive -E segment.

But even the enterprise parts only have higher TDPs due to higher core counts - the cores themselves are the same as the consumer desktop parts, with a bit more cache thrown in and some transceivers to help scalability to even higher core counts that we don't want. Nobody is trying to design the fastest quad-core processor, let alone dual-core or single-core. No one is willing to commercialize a chip that is 10% faster at single-threaded tasks when it will be a fourth the speed at highly-threaded tasks, especially when the processor can self-overclock one core when it's the only one in use, thereby offsetting some of the core-count tradeoff.

They're different chips - the laptop chips get much better perf/watt than the desktop components which are comparatively sloppy. That power management hardware is actually somewhat expensive technologically.

It really has more to do with the customers. The people buying these chips by the thousands are Enterprise Desktops, and keeping power bills down is their #1 goal. The customers don't buy GPUs in these machines either, they expect Intel's to be "good enough."

Unfortunately, consumer desktop purchases are basically a rounding error to Intel's multibillion dollar balance sheets, so they don't build parts for that segment. Instead, they blow some fuses on their enterprise parts and sell them as "Extreme Performance", "Enthusiast Desktop" or whatever other euphemism they want to use for "overclockable" these days.