Hi Calvin!
1) Sleeve hitch was an option- there were quite a few implements that didn't require it. The Cub Cadet 3-point was even an option.
On your 149, the 'standard' part, was the hydraulic lift... the rockshaft, instead of being operated by a big lever going from your right hand down to your right foot, was operated by the small hydrualic lever. This rotated the rockshaft to lift the mower deck and front implements like snowthrowers, dozer-blades,etc.
The 3-point 'kit' consisted of a long bar which connected to the rockshaft (just under the hydraulic cylinder) and reached back to the back end of the tractor's frame. It included a big cast-iron bellcrank with about a 1" hole facing back, and a pit to slide into that hole. Lastly, there was a pair of U-shaped metal straps 1/4" thick sandwiched together to provide two mounting tabs to hook implements to.
It was to these two tabs, and 1" rod, that the 'sleeve hitch' connected.
The Cub Cadet 3-point hitch was used for lots of made-for Cub Cadet implements (*I believe, and others please verify) that IH-CC actually made very few implements, but had quite a few made by OTHER manufacturers, then given IH colors and emblems, sold BY IHCC. Still more yet were made by others (like Brinly) and sold under the original manufacturers' names, but illustrated and marketed through IH Cub-Cadet brochures.
2) re. Loaders: IH didn't make a loader for the CC, but you'll see all sorts of brochures (IH and others) that show Kwick-Way, Johnson Workhorse, and other loaders fitted to Cub Cadets of many different models. I believe the reasoning was that IH-CC was in the business of manufacturing, marketing, and selling small tractors, so they built tractors, and enhanced the desireability of their tractors by making them plenty capable of physically accepting, and also surviving the attachment of implements, and then working with implement manufacturers to get good implements available for their tractors. They let the implement manufacturers do what they do best, and IHCC concentrated on making a good platform for accepting and working those implements.
You'll find that there's quite a few drawbar- and sleeve-hitch implements that're out there, many are really good, but some are just too light to survive. Where these IH-CC machines are built using the F-cub's cast-iron transaxle, heavy frame and powertrain, your average 'garden-tractor' of today is merely 'lawn-tractor', a toy, or overglorified lawn-mower by comparison... not really built to do 'ground-engaging' work. Attaching implements to lightweight machines means the implement will likely never get worked hard, and after being worked once or twice, will probably be hung up and ignored... but if you hook that same implement to a Cub Cadet, you'll find that it'll get torn into pieces in short-order. The IH-CC was truely a 'tractor', begat by scaling-down of an agricultural platform.