Remember, holding is also using.

Millions? Thats stretching it a bit. top 1% hold 90% of all BTC. 18 million wallets once you remove dust.
You can chalk up to that all those that hold couple dollars.
What are you left with?

What i dont get is why you would assume that most of those that are holding are using it as a store of value. It could be equally (or more so) the case that they hold it as a speculative investment.

I expect only the most savvy of Reddit users to use it.

Thats the question though. How will Reddit present it. Your concern might be distribution etc. (which is fair) but i think the first hurdle is "how do they present it"?
If its something they mention briefly and move on then it might as well be a BTT 2.0.

BTT is still in its infancy with no real utility

BTT has a real utility. It rewards seeders of copyrighted content (99,8% of all Bittorrent traffic) with a few cents for seeding. It pays you to violate the law.
I cant say much about their future plans.

BAT is something im looking at right now. Brave was a bit dissapointing so far. My experience is that its quite slower then Chrome, at least for me.
The thing about users and those that utilize the token and blockchain can be quite far off.
If token price, token transactions, token usage is not affected by project user numbers then maybe the project that launched the token doesnt really need blockchain tech