Don't forget that SPTYKS lives in America, and over there, Kirby are held in very high regard. They are also cheaper to buy in the US, and more Americans have thick shag pile carpet which Kirbys are excellent at cleaning.
I have a G7e and a Sebo X4 Extra, and whilst both are just as easy to push and pull, and do a great job on carpets, I have to agree that the Kirby is more inconvenient to use the hose, and is a great deal heavier to carry than the Sebo. The price of a new Kirby in the UK is astronomically high, and with tales of dreadful high pressure salesmen hassling old pensioners to part with their savings, Kirby are just not held in high regard here.
I like Kirbys, but I don't like their sales tactics. They are a top quality product, there's no argument there, but people nowadays want versatility combined with convenience. The Kirby is VERY versatile, but not the most convenient.