Why do people insist that in order to re-assemble a modern multi-group lens that one has to have fancy equipment for realignment of elements when the lens itself has no such facility for even adjusting groups relative to each other?

Take any typical prime lens and you'll notice the same construction paradigms in use:

1. Common outer barrel that multiple groups, usually front and rear, slide into and are secured with threaded rings - almost always accessed by a lens spanner.
2. Individual non-cemented elements being secured within a mechanical group via threaded rings and machined inner-barrels.
3. Absolutely no facility for adjusting any of the elements relative to each other. No set-screws for offsetting element alignment, fore/aft, etc.

About the only adjustment I can see is individual rotation of elements and how that might affect light relative to other elements. Other than that it seems as if the ultimate "alignment" of the lens as a whole is purely determined by the machining tolerances of the barrels each group fits into.

What am I missing here?