. . . due to access issues.
The largest measure of Omega's credibility is due to the success of their fabled 30 mm movement line, inaugurated in the late '30s with the seminal cal 30, which in turn produced several generations ending with the cal 7xx line in the late '60s. These movements were not only impressive technically, outscoring competitors in timing competitions during the late '40s, but also aesthetically. When the 10xx line of movements was introduced around the same time as the 7xx were being phased out, there were technical issues that resulted in a revision within a short time. Not that I have any personal experience with these movements, but from what I've been able to gather, the degree of difficulty in repairing damage due to aspects of the initial design can be greater than the ability of an average watchmaker to handle if the requisite parts aren't available. This consideration doesn't apply to the movement in yours, but the reported problems did much to lessen the enthusiasm of Omega collectors.
I suspect the more relevant reason, though, is aesthetic. The cal 10xx are, frankly, crude in comparison. That's not to say they're crude functionally, but rather, in terms of execution. Compare the regulator of a cal 10xx to that of any 30 mm movement . . . you'll see what I mean.
Admittedly, that's a shallow reason . . . but then, a larger measure of our predilections are due to aesthetics than many of us are willing to concede.
Cordially,
Art