I agree the difference is small - though this is an enthusiast forum, so there'll always be those seeking the absolute best performance. DDR5 is the absolute best for gaming, as long as you get a kit that can do 6000Mhz+. Is it worth it for the majority? No, though the cutting edge in technology has never been the best performance per $ available, this generation is no different.
Also - if you're willing to lose performance using DDR4 vs DDR5 (remember those reviews are using 4000Mhz DDR4, which not many have, 3200Mhz 3600Mhz is slower again) then why get the 12th gen Alder Lake, when Ryzen 5000 series is cheaper, and just a few % behind? Or the 11th gen i5's, i7's, which are also just a few % behind.
Additionally, this generation throws a spanner in the works, by supporting Rocket Lake as a drop in upgrade on Z690. Knowing this in advance, many have chosen to get a motherboard that supports DDR5 from the off. DDR5 boards will hold their value far more over DDR4 boards down the line. A £250 Z690 DDR4 board will not be worth much when DDR5 is cheap. More importantly though - who wants to swap out a motherboard to upgrade to DDR5? Far easier to get a DDR5 board from the off if it's in one's budget.