Any controls that do exist on the real amp are set to where whoever programmed the defaults or the preset thought it sounded good.
Just that sometimes the defaults are pretty, pretty bad IMO (and it's not just my opinion by far). When you click through the amp+cab list from the top, using a medium output guitar, there's not one clean amp until you reach the Jazz Rivet. And it doesn't stop there, whomever did this seemed to have tried to make high gainers ouf of, say, the Tweed Blues and several others. IMO that's almost factually/historically wrong. Sure, these amps have as well been used to be cranked up the Wazoo, blooming around and all that - but pretty much everybody knows that they really shine when used in lower gain settings, especially in the delicate breakup area.
And while they possibly tried to make Neil Young proud with all those cranked, farting vintage machines, they also don't exactly lend to trying out the (partially excellent) dirt stomps, simply because an amp that is about to melt down will eat their character for breakfast.
One of my personal hot candidates for "the golden raspberry award of presets-gone-wrong" possibly has got to be the Brit J45 Nrm.
Anderson with a Duncan Mini HB in neck position (medium output, medium bright):
Yeah, that sure sounds like "wow, let me explore this device further!"
And really, it's like that with pretty much all defaults. Now, personally, I actually *do* know how to change things so they work, I also saved my own defaults (and quite some base presets) - but that's not what you do on first contact, even less so when this is your first contact with the modeling world.
Having said all that, it had gotten quite a lot better with the latest updates and their amp additions.
But still, if you want to get an idea of what most of the amps are like, you need to at least grab the Drive knob and pull it way down.