One problem with the 10mm is the choice of platforms.
First they are all big guns. and most are expensive 1911's - and not everyone is a 1911 fan (and I know plenty of 1911 fans who wouldn't want a 10mm 1911 if it was given to them) or wants a single action gun. Also not everyone wants to pay the big bucks that these guns are priced at.
Only Glock and EAA have guns at reasonable price points. Even the Delta elite is $800 and up usually. The rest are 1K and up...limits appeal for many. Add in the hard to find, often expensive and mostly watered down factory ammo and the round has even less appeal to the vast majority of shooters.
The 10mm is a round that begs for reloading and as a moderate sized critter gun in automatic it is hard to beat, especially the Glock for backpacking.
At one time back in the day I had both glocks, the SW 1006, 1076 and 1066, the Star Megastar (what a beast) and a Bren Ten special forces Dark, I even carried the G29 and the 1066 as my EDC. I was a huge proponent of the 10mm but several things detered the round from being what many hoped it would be and after the FBI ditched the 1076 - interest waned and currently no government agency (except the Danish army which issues them for polar bear protection in greenland patrols) issues the 10mm. (some may authorize it but that is not the same, thus gunmakers seem to have little incentive to make new 10mm guns.
I have moved on from the 10mm as other guns offer many advantages over the 10mm. If I lived say in alaska or some western states I would still have a 10mm, but in Florida the 10mm serves no real purpose for me.
None of the major ammo makers make their police oriented ammo line in 10mm (Ranger, HST, Gold Dot etc...) when they do then I will believe its catching on again. Didn't Dan Wesson drop most of the 10mm guns from its line? Not exactly a positive sign. And after the Vltor "New" Bren Ten (Fortis) debacle I have my doubts.