OK. You are very confused. I'll lay it out for you.
Why do buyout clauses exist? The club wants to receive a fair transfer fee when the player is sold, but the player wants the flexibility to be able to change teams without waiting for his contract to expire. The buyout clause is a way of satisfying both of these: the club agrees that the clause is an equitable price and obligate themselves to sell at that price, and the player agrees to sign for a club that's perhaps a little below the level they would ordinarily sign for, or that they are unsure about, or for perhaps a longer contract than they would otherwise as they have a way out that the club has effectively already agreed to. Like every contract term, it's a compromise between both sides that meets their mutual interests.
In Spain, it's obligatory to have this clause for some reason, but that's easily circumvented by setting it to an absurd amount of money, like a billion euros for Cristiano Ronaldo.
It's also worth pointing out that the buyout clause only sets a ceiling on the transfer fee. Ba's transfer clause was 7 million pounds. If Newcastle wanted to, they could have sold him for 5 million pounds, for instance if no one was willing to bid the 7. Reasonable transfer clauses do tend to set an anchor on the player's value, which might confer some negotiation advantage to the selling club, but obviously there's a benefit to the buying club when they would be willing to pay more than the transfer clause. Ba is a good example of the latter case.
It's also worth pointing out that the player actually has to sign for the buying team in order for a transfer to go through, which means a lower buyout clause is always in the player's favor. If Demba Ba really didn't want to play for Liverpool, but Liverpool somehow came in with a 7 million pound bid for him, he could just say "no" and stay at Newcastle.
Why don't we see tons of players with buyout clauses that are essentially nothing? Well, with due respect, because that is maybe the stupidest thing I have heard on this sub. Why on earth would the club agree to that? The players don't draft their own damn contracts! They have leverage, in certain cases, that helps them negotiate better terms, but the club is the one who is offering the contract to the player.
Basically, you are just wrong on this one. Not just wrong though. You don't understand the fundamental workings on contracts, which is hilarious because you've chosen do act like a dick over it.