I have barely seen ThunderBolt 3 Motherboards at all. Early info was that Gigabyte had monopoly of Alpine Ridge supplies, but they don't have a lot of TB3 Motherboards, either. Not sure if we're going to see them more often.
Personally I would love to get Alpine Ridge even if I'm not using Thunderbolt. The good thing about this generation is that Alpine Ridge doubles as a USB 3.1 Controller with Type-C ports, and I would always pick Intel first party controllers over third party ones like ASMedia. So you can see it as two premium USB 3.1 Type-C Ports, with the TB3 capabilities there just in case you eventually get Hardware that uses it. I wouldn't miss it on a high end Motherboard, sad that they're rare.