This has the same solution as any other story around copyright infringement. If you provide people with easy, convenient, legal methods to consume the content in a way that works for them, for a price they find reasonable, then they overwhelmingly won't resort to illegal means. I'm not saying these bars are correct to resort to illegal streaming, but a wise businessperson would see this as a signal that their product…
I think the problem with your statement is "for a price they find reasonable." Because the price some find reasonable is much lower than others (the very reason why demand curves are downward sloping is they there are different willingness to pay for different customers).
Since La Liga can't price discriminate easily and charge those with higher willingness to pay more AND since they have a monopoly over these games, the rational economic decision of the league is to keep the prices at a higher price, which while unfortunately resulting in fewer people having access, it also means more profit for them.
Thus, I don't think it is as simple as you are making it appear.