On most reconstructions of theropods I've seen, they have either protofeathers or true feathers. Heck, I've even seen em' on Eoraptor. But I've never seen an illustration of spinosaurs with them. Is this because we're sure they didn't have feathers, that we presume they had feathers even though we haven't found any because most other theropods did, or that since we're not sure they had feathers so we play it safe and leave the feathers off? Maybe the artists thought covering Spinosaurus with feathers made it look like a silly, oversized chicken.

Whatever your answer is, thanks!

We have evidence of some form of feathers all the way down to the base of  coelurosaurs in the theropod group. However, spinosaurs, while they are theropods, fall outside that group. We currently have no evidence for feathers existing that far back in the theropod family tree and Eoraptor is even farther out. So putting feathers on spinosaurs would be purely speculative without any evidence for it and Eoraptor would be rather far-fetched. We might expect to see feathers on young tyrannosaurs, but not allosaurs, spinosaurs, ceratosaurs, or herrerosaurs, which are all less derived than tyrannosaurs and the maniraptoran dinosaurs.

I'd disagree there a bit Joe. It's speculative yes, but it is based on the idea that the protofeathers of various derived theropods is homologous with the filaments seen in ornithischians like Tianyulong and / or even the pycnofibers of pterosaurs. This has yet to be examined in detail but is possible. If so, it's likely that many basal theropods also had protofeathers / fibers of some kind in the skin. There is certainly a degree of 'evidence of absence' here since we simply don't have skin impressions / fossils from areas of exceptional preservation that might show fibers and filaments for most basal theropod lineages.

I agree there is no good direct evidence for these in thinks like ALlosaurs, but I don't think it can be ruled out as yet.