LOL
The only "should" surely must be premised on whether the cost-benefit of implementing it makes business sense to Garmin to invest the effort and resources as the implementor and commercial service provider (even if right now Garmin Connect is provided free of charge to users of Garmin fitness devices).
Users will always welcome more flexibility and more features, especially when it doesn't cost them anything more either upfront or to access such on an ongoing basis. Yes, I've seen people whinge about seeing golf features when they don't play golf themselves, but they're not asking for those features to be discontinued, but merely ask for more functionality -- specifically, the ability to hide those features by individual user option -- free of charges again, of course. That's not a good basis for testing whether something "should" be available.
even if right now Garmin Connect is provided free of charge to users of Garmin fitness devices
Connect is one of features, they advertise it on a box of devices. You get it with a device for which you payed, so hard to name it "free". It's included in price.
The same way you could name firmware "free", but that's strange to split software from hardware. It's one box with one price for all elements.
What's more, some devices request syncing with Connect for normal functionality. For example, you can't set date/time without it in some simple watches.
Nevertheless, access to Garmin Connect is free of recurring subscription charges, so there is no revenue stream coming from it to warrant investing in additional features, or data interchange/integration with foreign systems owned by entities with whom Garmin has no commercial agreement or partnership, unless the lack of such has proven to be retarding sales of the Garmin fitness devices because those third parties have a much stronger foothold in the fitness tech market.