Because that's the last hope this game has. If the top player will keep using the same braindead decks too, there will be no one left soon to at least try something new.
And fresh decks might actually work better. Because with the "meta" ones even I can recite them by heart (despite never seeing a full decklist for any of them) after being woken up in the middle of the night. And everyone in the pro league surely knows those decks and ways to counter them by heart. New combos can put your opponents off enough to give the the edge in the match.
I vaguely recall those being famous football players? Then you are wrong. The same would be "I hope they won't bring people with baseball bats on the field to break to other team's players' legs".
As much as i would also love to see original decks, in this tournament or anywhere in Gwent really, i dont have my hopes up.
The problem of metadecks, why they are so strong, is that even when you know exactly what cards your opponent has, its still hard to beat them.
And you can tech against a specific metadeck, but then it will perform worse against other metadecks.
And if there's one deck that is tier 0, so strong it beats all other metadecks, its no problem for tournaments, its simply banned by everyone.
What you suggest wont happen because the selected choice for Gwent e-sports is open decklist, so all opponents know exactly what their opponents will have. I think this is a terrible choice, which makes these events way more boring and demands less skill from competitors, but it is what it is...