Why do you think their service is not about buying or selling BTC/ETC?

those[1] are the screenshots from the app as I navigate between the tabs. not that I am expert, but to me it is quite similar to the options gambling.

the Spot Trading, the Perpetual Future are easily falling into the gambling category.

See, while a professional trader might use these tools for complex hedging strategies, for the average person, entering the "Perpetuals" market with leverage is a high-risk bet that can lead to rapid and total loss of funds, much like a casino. And let's face it. Vast majority of Coinbase users are most likely not professional traders.

[1] https://photos.app.goo.gl/de7ygKYvpq64p8nm9

I have never used anything except Spot trading, and it is just the regular way to buy some crypto, I have no ideas how else are you going to buy it. The third screenshot is very familiar to my experience with different Currency Exchanges. You need to input some funds to the CX, then you are choosing how do you want to exchange it, then if the market is ready for your deal you get what you have requested.

I do not see any gambling if you are going to post for example your desire to buy 1 bitcoin for your 1 dollar. As they say, "There are two fools at the market: one sells, the other buys" so you are free to sell your 1 dollar for any insane price, it is way better than having it on your Balance without any moving (because there is no warranty the CX will keep existing tomorrow, not your key means not your crypto).

Most CXs are proposing some complicated deals like to short some currency, or maybe some operation with leverages "that can lead to rapid and total loss of funds". Is this a problem for you to not use the instruments you aren't understand? Spot trading is enough good to have some profit with minimal knowledge and minimal risks.

Liquidity.

How is it aligned with https://news.ycombinator.com/item?id=45602192 ?

Also, if you can kindly share personally how it is assisted you with liquidity?

Not a customer and never was. But I know of businesses that accept payment in crypto and use CB to convert to fiat.