These discussions need to bifurcate between Conforming / High Balance Conforming, and Bank Jumbo Portfolio. Pricing still isn't too bad for Jumbo fixed.
ARM products are not "popular" per-se, but the choice of last resort for many. Banks and Agencies don't want ARM products in the face of rising Fed Funds and other ARM indexes. With the 6 month SOFR index around .106, and most Margins at 2.25, you'd think ARM's would run around 3.5 or so, but many ARM start rates are very high 3's, low 4's.
ARM's are still stigmatized by what happened in 2006-2009, but also due to the recent low rate environment. There is a strong pushback on ARM products. Some of the reasons? "Oh... my friend/co-worker/neighbor/(insert pronoun here) got a 2.75% 30 year fixed rate. I'm kicking myself for not acting sooner. Take an ARM that won't adjust for a decade? No Way! It could go up to thirty-teen some day. I'll stick with a 5.5% fixed rate" instead of a 4 percent ARM. Besides, I was told "you can always refinance". Blegh. Yes, a refi opportunity may come along. The view should be "possible" but not "always".
Few people standing around the BBQ of their new home like to tell their friends about what a great low ARM rate they got - even though it may be a wise way to buy. Fewer still are comfortable explaining to their in-laws why they took an ARM versus a fixed rate. I've heard these and other reasons from the very lips of buyers in the past 90 days. History, as it's been said, is a circle.
At this time the idea of a long term rate environment reset, even a medium term purchase price reset, hasn't yet imbedded within the collective buyer mindset - but these things are coming - hedge accordingly.
My .02c