I suspect given the size and shape of the Self-Sealing stem bolt props, they were probably used for major assemblies like starship or starbase components.
As for smaller items, I presume that because the industrial replicator can fabricate pre-assembled objects with complex part geometries, subcomponents and individual fixtures were deemed unneccessary (unless one wants items such as hand Phasers or tricorders to be repairable)
Of course, it may just be the producers' and art departments idea of a clean futuristic look by taking out fasteners that would look ostensibly like something out of the 20~21st Centuries.