Probably because it is the only digital scanner that can be had used for around $300. You will not touch a Uniden or a GRE for that cheap. And the fact that it really is not that bad of a radio. Just doesn't have all the newest stuff.
Many have stated on these forums that the Pro-96 decodes P25 much better than the BCD396T. I haven't seen a BCD396T yet, so I can't speak from personal experience, but the Pro-96 does its job just fine.
I bought my 96 for about 350 used but frankly I still use my Pro 97 more because it seems to pick up more frequencies. Unless your area is completely digital, it's not worth the extra money, I have found the sound quality between the two is very different and frankly, the only thing it picks up around here that the 97 doesn't is one CSP patrol and a couple of medical channels-NOTHING ELSE! I prefer using the 97 more frequently after setting them up side by side and seeing what each one picked up. Maybe someday, it will be worth it to me, but right now, the other scanner works better! Fortunately I didn't spend the entire $500 dollars for the thing.......I only bought it because it was such a good deal but I don't see myself using it exclusively for a while.
As stated above: The PRO96 has far better decoded P25 audio than the Uniden 396T & 996T.
Mine gets used just for P25 trunking with it's crisp clear recovered audio, especially as a base unit connected to an external antenna. The garbled noise and missed transmissions of the Uniden's soon became tiring and has seen them used a lot less. This is especially the case with the 996T which cannot handle a gain base antenna.
My 396T gets used as a carry radio because it has the close call function and the ability to properly track 800Mhz legacy systems- which the PRO96 can't (cell blocked nonsense).
Bought mine when they were $449, but now they can be had for as little as $300 thanks to certain agencies turning on the crypto.
The V-scanner function is nice too- switch back to an analogue profile easily!