It is a reasonable question, and a great idea. The simple reason the smaller ST is not offered is because the mfgs do not believe it would be the best use of resources. Are they right?
The motorcycle market in the U.S.A. is both cyclical and fickle. In good times when sales are booming, the factories have money for r&d & develop cool bikes. By the time they hit the market, sales have dried up, and the factories get stuck with the bikes. When times are tough, no r&d, and no cool bikes that the customers want. Vicious circle.
The 80's were a good example. Yamaha Vision 550 - 1 or 2 years. Honda CBX 1050 (as an ST) - 2 years. Honda Silver Wing - 2 years as a 500, 1 as a 650. Lots of standards (before "naked" was in vogue) came and went quickly, even with aftermarket fairings & panniers available.
Sport touring has proven to be a small market in the states. I personally cannot understand why anyone would prefer a cruiser or and adv bike to and ST, but those bikes are still selling, adv bikes being the "current thing". Personally, I think most of the adv bikes are just ugly ST's, but what do I know?
Economies of scale - it doesn't cost that much more to build a bigger car, bike, or whatever. In America, that usually results in us choosing bigger because it seems to be a bargain. Even if it isn't what we may really want.
Currently, a few examples - the Dullville, as previously mentioned. Had been available overseas for years. About as old tech as the C10. The Versys ST/ABS - only overseas. The Yamaha Fazer (ABS/fairing, topcase, taller w/s, tankbag factory options) Canada & overseas. V-Strom ABS - close, but marketed as an adv bike, Ninja 1000 - close, no abs or factory bags, Triumph - Tiger 1050, 800 & Sprint ST - all pretty close. BMW - 800cc range. Some of the other European bikes are interesting. So the possiblities are out there, and some more cool stuff in the foreign markets.
Ultimately, its a roll-your-own market until the factories see that their is enough market/profit for them to get involved. The Suzuki SV forums have a section for ST mods. Pehaps other forums do, too. Personally, I'd love to seen an SV900ST or SV1000ST - ABS, bags, full sport(y) fairing, adjustable bars, adjustable w/s, adjustable seat height & pegs, fully adjustable suspension, 5+ gal tank, decent seat(s). Or a Kawa Ninja 800/1000 with the same options, or the Fazer 8 with the same. The NT700 replaced by the NT800 with a hot-rod V-twin and the C-ABS off the CBR's.
As it is, nothing out there new is really calling to me. So I farkle w/ the stuff in the garage.