But Oblivion also has a lot of exposed concrete, so for The Smiler its a theming choice to make it look very industrial and partly in-keeping with Oblivion.
(Sorry you set off the architecture student in my brain!)
Interesting point, Oblivion's use of concrete is very well designed and was a key part of the theme. The design of the drop zone, and levels of the queue took a lot of effort and it really paid off. In fact other areas like the buildings around the queue aren't even real concrete, they were made to look that way for a particular style and a particular effect (although the effect has partly been removed & cladded in plastic).
Oblivion/X Sector got me so interested in retro architecture and there was a conscious design effort to reflect various (concrete based) modernist architectural styles to evoke the kinda Soviet, austere and curious theme.
However The Smiler's use of concrete was purely because of a big balls up with ground surveying (the queue and pit) and the cheap buildability factor of using precast, standardised concrete panels for the building. Why the concrete & blockwork was all left uncladded, even INSIDE in most places (awful), is a major cop out I think.
The "it suits the theme" idea was just an excuse for them to leave it looking that way, instead of designing something architectural with imagination & mystery like Oblivion (in its better days). I think it's terribly limiting, and the flaws will show up badly in a few years, if it doesn't make for a horrible and bland experience walking through the queue & building already!
Case in point, SW8's station is exactly the same precast concrete flat-pack box style, even though it's a totally different theme. Let's hope it is cladded somehow. There are always cost-effective ways to do a great theme, if a proper budget is given.
I think Merlin's use of architecture in all their projects is fundamentally poor. And I don't just mean style, I mean the basic shapes and layouts of their attractions are always so limited by their formulaic design. Especially Sub Terra, which needed a shipping container add-on to even have space for any kind of ending (this is a joke); Derren Brown's GT, where what could have been a great reveal of the train in the auditorium is only seen from awkward 90 degree angles, no sense of scale of level; or The Smiler's blocky, empty blockwork indoor scenes. A whole range of wasted opportunities.