Official 
post (which disavows Roger Craig Smith)
Seriously why. Sonic and the Black Knight was the last one and it was also the last time you could beat the final boss to a kickaas buttrock theme song. Why don't we have this anymore?
I really liked it when it came out. A lot of Sonic games get lost in the sauce trying to do too much, but BK is in the camp of "do one thing decently well for a decently long campaign". The English voice acting grates on me in the worst way but you can set it to Japanese so that stops being an issue fast, plus if the gameplay clicks for you iirc there's a ton of side content to play. My general take is that Sonic games are better than people give them credit for and I think SatBK is a solid 7/10