Because those kits are fricking hideous?
Perhaps the British flag is a bit too 'busy' to pull off a Scandinavian-style full-body cross, but I guess they could at least have sleeves with the flag on. I don't see too much of a problem with the jersey, after all the Dutch national champion has a full tricolour jersey so they don't get confused all that much, unless somebody designs a kit incorrectly (like Bole's Slovenian kit that was actually Dutch).
It's nice to see a Movistar champions' kit that actually pays some kind of respect to the national jersey (the same team, in days of yore, presented a more obviously British jersey for Jeremy Hunt. I'll see if I can find it), although I believe this is more because the British have fairly strict rules about their national champions' kit (perhaps because of the aforementioned Hunt kit). It's why I was astounded they were allowed to keep that chronically bad kit they gave Visconti last year, even if it wasn't quite as bad as the Bulgarian Champions' kit that Katyusha gave Pippo Pozzato originally.
Here we go: Jeremy Hunt's jersey at Banesto. Didn't take much googling: