Plenty of river stretches are run on a commercial basis....... Some managed river stretches are seeded with stocks of non-indigenous species... e.g. Barbel, Chub, carp and grayling... presumably this is offering 'what anglers want' - which is the commercial mantra.
The EA has tightened up on licensing, a local club looked into stocking barbel - thankfully this was declined. I like barbel, but am more than happy to catch the very occasional Barbel from other rivers.
Rivers normally offer a bit of every thing.... a few carpark swims, a platform or two... and expanses of less managed sections.
I like the unknown quantity side of fishing rivers.... even well established commercial lakes are throwing up the odd surprise.
But a river stuffed full of F1's and pasties? No thank-you......