I have often considered that the Imperium runs on technology driven by "Imperial Standards"  analogous to current US "military standards".

For fictional example, MIL-STD-123456 identifies types of shovels, and this shovel complies with MIL-STD-123456.5.A

Presumably, the megacorps either use the same standards, or for some internal things, their own standards, to ensure that everything is maximally interoperable.

Which means, since the Imperium itself is a huge consumer, any equipment marketed to the various branches of the Imperial government will tend to conform to the relevant imperial standards.   This tends to drive some level of uniformity to the equipment.  

A lot of larger institutions will tend to adopt IMPSTAN values, either because they see it as guaranteeing some minimum quality level, or 

OTOH, planetary governments and smaller, single planet businesses, are free to use whatever they want.  

Their gear tends to have a little more variety.  It may or may not meet the Imperial standards, or they may just not have tested it.

Local stuff may be smaller, lighter, and "better" than equivalent Imperial gear, but it won't necessarily work on the next planet over.

Or the Impie gear may not work on the local network, once you get out of range of the downport or your ship.

YMMV.

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