Interesting! I play a Link 7* and struggle with anything smaller than a #6. I do tend to agree that the majority play a 5 or 6 but there are plenty that play bigger though. Here's a few:
John Bambridge Arbex - B 7*
Gary Bias Custom Beechler Bellite #8 Diamond Alto #M8S
Dave Boruff Beechler Bellite Alto #8
Nick Brignola Runyon Bionix 8*
Paul Carman Beechler Diamond M8S
Kent Engelhardt Beechler Diamond S7S
Rocky Gordon Beechler Bellite #7
Euge Groove Beechler Bellite #7 and a Beechler Diamond M7M
Craig Handy Berg Larsen 105/1
Everett Harp Beechler Custom Bellite #7
Ray Hutcherson Beechler Diamond M8S
John Klemmer Metal ARB #7
Dave Koz Metal Beechler 7
Oliver Lake RIA 7
Joe Lovano Otto Link 9*
Joe Lulloff Beechler 7 (amongst many)
Derek Nash Beechler Diamond M8S
David Sanborn Dukoff D7 and D9
Tom Timko Beechler Diamond M7S
Chris Vadala Meyer 7
Rocco Ventrella Beechler Bellite #7
Ernie Watts Lawton 9*, Barone Metal
Having said that if just starting to play an Alto then I agree that a Berg Larsen #8 might be difficult to control, until those chops get used to it!