Because the 3050 is the ultra-entry level card from nVidia, and the 6500XT is AMD's ultra-entry level (as there is no RX 7500 on the market yet). Also in terms of performance the RX 6600 and RTX 3050 8GB perform on par, it is not "64% faster". With the creation of this 20% slower 3050 6GB variant it will compete against the RX 6500XT with the 8GB version remaining to compete against the 6600XT, with $180 pricing for the 3050 6GB confirmed via listings (including one on Newegg), and $140-$200 for the RX 6500XT 4GB.
Those are mixed raster and "DXR Ultra" results. The 8gb version of the 3050 struggles to pull 30FPS at 1080p in ray traced titles that came out in 2022, so neither card is likely to deliver a good RT experience in 2024.
In non-RT results, the RTX 3050 8gb scored ~85FPS in a purely raster average. Minus 20% for the 6gb would be ~68FPS. 111.2/68=163.5%.
And you can declare the 6500XT and the 3050 6gb to both be "Ultra-entry level", but when you fill in the other matchups that puts Nvidia about $40 off in pricing at each tier. It's easy to "win" the tier if you're priced closer to the next card up than to the one you've decided you want to be compared to. I'd say tiers fall more like so?:
RX 6400 ($125) versus Nvidia no-show* versus Arc A380 ($120)
RX 6500XT ($140) versus GTX 1650 ($160)
RX 6600 ($200) versus RTX 3050 6gb ($180) versus Arc A580 ($180)
RX 6600XT ($240) versus RTX 3050 8gb ($247) versus Arc A750 ($220)
* There's technically a single model of GTX 1630 for $135, but that card seems to have never been stocked in meaningful numbers.
Prices are from Newegg for the lowest priced new version of the card as of today.
No power connector is nice, but unless you're up against the limits of a PSU that you can't upgrade, this is a regression in price/performance over cards that launched 2 years ago, and doesn't make sense outside that niche.