I grew through what you're referring to regarding different powders...but unfortunately threre are real, practical considerations that affect 99% of anybody who might want to try muzzleloading, and you probably already know them.
Real black powder is almost impossible to find on a local basis but subs like Pyrodex are available everywhere...and to be honest, Pyrodex actually works very well...used it for years before I switched to flintlocks & Goex...so there's not a lot of incentive for the occasional ML'er to even think beyond buying a Lb of Pyrodex at Walmart.
The average guy has no insight into ML/BP suppliers and mail ordering, etc...and if they do, it's a rare place that will sell less than a case of real BP at a time anyway;
And the average guy starting out may only take a ML out a couple times a year, only hunting a ML over one weekend of a short special season so he's not going to lay out $225+ dollars for a case of something...I didn't when I started.
It's only if muzzleloading really gets in your blood and you start shooting a lot, subscribe to magazines, find ML message boards, learn about real BP, etc, that you're more apt to make the switch to real BP, start thinking about case prices, etc...I started in the late 80's and as of this year 2004 still do not know anyone locally who shoots a ML year round like I do...they pull out an inline or a TC Hawken for a Saturday before the regular gun season starts then reach for their .30-06's.
Back when I started I was drawn into it by all the marketing hype about inlines and BP subs, and that same hype about "modern powder for muzzleloaders" actually implies that real BP is inferior, dirty, dangerous, etc...I wasn't even sure if real BP even existed any more, assumed it was outlawed, etc.
The good news is that the marketing hype and BP subs have drawn untold thousands and thousands of people into muzzleloading that never would have thought about stepping into it otherwise, and like me, some may get hooked, shoot a lot, and start buying real BP by the case...but most occasional muzzleloaders won't for all the reasons above.