Those are staking pools, which represent thousands of individual users, and the largest one (LIDO) also has has additional decentralization that is not well captured by looking at just reward address. The reward address is a contract that individual users will be able to tap into.
Worth adding it's also not substantially less decentralized than PoW mining was, the status quo was 41% of hash power controlled by 2 pools. At least now it's using significantly less power and is largely more non-custodial.
I think you have a misunderstanding of how the protocol works. At no point do your assets "go into the relay." The relay only takes your signed orders (not the actual assets), and the tokens literally do not leave your wallet until the time the trade is executed. No trades can be executed unless they have a signature generated by your private key.
Or they can verify them themselves since it's all open source. And for the less technically inclined there's also 3rd party audits and an active bug bounty. Point being, everything is open and transparent, and none of it happens behind the scenes, so that's where the "trustless" comes in.
While yes, that word is overused and misunderstood, and regular users still admittedly do put trust in open source code on a public network, it's a much more open system than we've been able to have before. The trust users depend on in this instance doesn't rely on faith in any single entity to tell you what's changed in their private DB behind the scenes, you can verify it for yourself.
While I agree many of these apps have their values overly inflated if you look closely at their usage, I think measuring web 3 apps with web 2 metrics like DAUs is a bad premise. Most of these services arent replacing social networks or content providers, but are instead providing financial instruments (which users spend a high amount of value on, but don't necessarily use every day.)
Augur may not have a high volume of pure users but there's still a decent amount of money on the line in markets at any given time (1.1 million in USD, at time of writing, according to https://predictions.global/)
Then why does this footnote exist on the google store?
See the last sentence:
¹The Google Assistant on Google Pixel Buds is only available on Android and requires an Assistant-enabled Android device and data connection. Data rates may apply. For available Assistant languages and minimum requirements go to g.co/pixelbuds/help. Requires a Google Account for full access to features. Google Translate on Google Pixel Buds is only available on Pixel.
Worth adding it's also not substantially less decentralized than PoW mining was, the status quo was 41% of hash power controlled by 2 pools. At least now it's using significantly less power and is largely more non-custodial.