[greglindahl]

Segmented SRBs are used on Ariane 5 and Northrop Grumman's upcoming Omega rocket, while Vega, Vega-C, and Ariane 6 will use a single-segment SRB. It's a choice that was dictated by politics for the Shuttle, but it's also a choice that can be made for other reasons, like a smaller composite segment using a cheaper tool (Omega and the Boeing 787 fuselage tube).

[TeMPOraL]

In general, "need to be segmented for transport" is not necessarily a political thing. Russians have the Proton rocket which looks as if it had boosters bolted to it, where in fact those are parts of the first stage. I heard recently that the reason for this design is precisely because if those side parts were internal, the rocket wouldn't fit on a railcar.