Probably because it isn’t a rim designed for tubeless. I have been racing several seasons on 22ish mm wide wheels (Stans Valor and Podium) with 2.2-2.4 tires and have yet to burb. Even when I was near flat before a leak sealed I still didn’t burb, and I attribute that to the rim design.
I (145 pounds) can’t get away with anything less than 19 PSI on my XC bike on the front, and prefer closer to 25 in the back. Anything less and the handling goes to shit and/or I start to bottom out the tires on the rim. Coincidentally I run very similar pressures on my Enduro with 25-29mm wheels with Double Down casing tires. I trash a rear wheel about every 3 months too