For many, it's the lack of being tied to a subscription based software model...
Yes, and the price is probably more affordable that an eternal money tap.
It also has a number of more innovative controls than LR or PS, and it's made with the use of GPU acceleration in the basic design, which should allow a responsive system, e.g. with a (growing?) number of Live filter layers that update instantly as their controls are tweaked.
Of course, things start with a good Raw conversion, and that's where it is currently lacking a bit in my (spoiled with Capture One quality) opinion. The apparent option to choose a Raw conversion engine is promising, but I'm not sure which options will become available. Apparently, on the Mac OS version, there are already several options available but I do not know which, and how they differ.
Raw conversions can be opened as 32-bit HDR files, which would allow lots of postprocessing with reduced risk of quantization artifacts (e.g. posterization). Chromatic aberrations seem (needs to be confirmed) to be corrected before Raw conversion/demosaicing, which would be good for a higher resolution Raw conversion.
Cheers,
Bart