44-40 is not an "anemic" round -- at least, it doesn't have to be. I load and shoot thousands of 44-40 rounds a year. Most are pretty mild, as I use them for cowboy action shooting. It also makes a fine hunting round. In appropriate (Ruger) single action revolvers and in some rifles such as the Winchester 92 and clones, you can load the 44-40 to near 44 mag levels. It has the case capacity for it. The limiting factor is the strength of the gun you're shooting it out of.
On that last point, keep in mind what someone else already said above -- the 44-40 was invented by Winchester as the .44 Winchester Central Fire (.44WCF). It was introduced with the model 1873 rifle, and replaced the .44 Henry rimfire round that was used in the 1860 "Henry" repeating rifle and the model 1866 (the so-called "Yellowboy" rifle). Compared to the 44 Henry, the .44WCF was pretty potent.
While the Winchester model 1873 was a "new" rifle, it still used the same toggle link action that was first successful in the 1860 Henry. It is NOT a strong action, and cannot handle a lot of pressure. The 44WCF was designed for that action. If it was loaded to 44 mag pressure levels and used in and 1873 Winchester, it would blow the bolt out the back of the receiver and blind or kill the shooter.
Winchester came out with a much stronger action in 1886. It was a John M. Browning design. In 1892, a scaled down version was introduced for small cartridges like the 44-40. The 1892 action has dual locking lugs and can take very high pressures, including heavy 44 mag loads.
The "thutty-thutty" came along even later, as I recall, first being offered as the .30WCF in the new Winchester model 1894. As others have pointed out, it was the first successful nitro (smokeless) cartridge. While there are reports that some munitions companies did load the .30-.30 with black powder, it was never intended to be so loaded, and it's an awful black powder cartridge. It lacks sufficient case capacity, and the very small bore gets fouled very quickly. Successful black powder cartridges either pack tiny powder loads (like the .32-20) or big bores (.44-40, .45-70, etc.).