Why didn't IBM ship OS/2 with its own computer models?
That is actually a very complicated question, that I will attempt to answer briefly.
There were two, completely separate, divisions in IBM. One handled building PCs (and they were originally responsible for having Microsoft make the BIOS, and DOS). The other handled software development, other than DOS. Rumor has it, that they were across the hall from each other, but I don't think that was true. The IBM PC was always looked upon as being a "toy", by upper management, and they pretty much ignored anybody who said that it had a lot of potential, if it had a proper operating system. Somehow, somebody did manage to get both projects off the ground, but the two divisions hated each other, and would never cooperate. IBM actually made a pretty good PC, but others came along and made them cheaper, with better support (remember, the PC was just a "toy", so upper management didn't care). Meanwhile Microsoft was learning a lot about how to make software work, and OS/2 made a pretty good base for something cheaper, so Microsoft made sure that they owned a license to use whatever OS/2 had. They also contributed a few things to OS/2, just to be sure they had a foot in the door. Eventually, Microsoft walked out on IBM, and created windows (much to the relief of the PC department, because they had an outside alternative).
There was also the legal problems with bundling software with a PC. IBM was flat out not allowed to do that, while Microsoft engaged in a kickback scheme to get all manufacturers (including IBM - remember that the PC department hated the OS/2 department) to install their software. IBM did manage to install OS/2 on some machines, but windows was always what came up first, so most users didn't even know there was an alternative, or they figured it wasn't worth the effort to even try it. Knowledgeable businesses did recognize that OS/2 was superior, and many did embrace it. At that time, IBM did try advertising OS/2, but that fell flat on its face because they had no experience with selling to the general public (and, the marketing department didn't believe it would ever sell anyway). Meanwhile, Microsoft did a very flashy advertising program, aimed directly at young people. IBM went back into their shell (still believing that the PC had no future), and Microsoft basically took over the PC world. Eventually, the IBM PC department was sold off to Lenovo, and IBM decided to abandon OS/2.
It is an interesting study, to look at what the IBM share prices did, over that period, and upper management still looked upon the PC as being a "toy" (probably still do).
Here we are, 25 years later, still trying to make OS/2 work on modern hardware. Fortunately, the OS/2 base was well designed, and it is possible to fix many of the long term problems, and add new features. The main problem is that we just don't have enough people, who know what they are doing, to keep up with the demand, and there are licensing problems with the IBM development tools, which makes it difficult for a programmer to get started. Most "new" development is done by porting software from the Linux world, which has introduced it's own set of problems, but it does keep the platform alive.