Ok so I like to look at peoples creations, I also like to see what the best way to destroy those creations are. Elements under the radioactive tab have some pretty destructive (if not laggy) effects. Out of all the bombs I've made, the most destructive is almost always made by making medium sized circle out of brick, filling it almost completely with EXOT, and then clicking and holding the mouse button with ELEC selected. the effects are devestating. The only reason it can think of is space, and if thats the concern if you cool down DEUT with the cool tool (or using LN2) you can put alot of it in a small space and (assuming you've cooled it to where it is glowing) just a couple protons can cause TONS of damage, so why no bombs like these?
Intersting concept.
You said, the reason is space. How will you destory a city with a huge brick circle in the middle of it?
I think part of it has to do with size. The thing is, while EXOT bombs can make a decent explosion, they don't seem to be very efficient in terms of size needed to get a good explosion. For comparison, exploding SING bombs can provide a massive explosion from a bomb smaller than the thickness of the walls used in your EXOT bomb. On the other hand, the azure lotus bombs use exploding EXOT, but they combine it with GBMB.
I once made a huge bomb using EXOT, which can get you infinite fusion, meaning 256 pressure and 10000K temperatures, but I'm sure it can be made smaller.