Prosecutors aren't necessarily blessed with bigger budgets in a lot of places, they simply have a separately-funded (and very well funded at that) investigative body that is the police or sheriff's office doing the really expensive part that the defense, especially a public defender's office, will only have a skeleton crew to do. The problem is that defense may not have the resources or knowledge to use inadequacies of something like this as a defense in the first place, and may not be able to effectively cross or direct an expert because of the lack of specific expertise and the reactive nature of the job.

It's not that the venn diagram of tech-literate and criminal-defense lawyers are entirely separate circles, but having been "that guy" in a public defender's office for even basic stuff like cell tower triangulation accuracy to finding proprietary surveillance video codecs to decode exculpatory evidence, you really need to start at square one while the prosecution have the whole police department's resources, expertise, and initiative at their disposal. You can afford the expert, it just won't do any good when you don't know what questions to ask that will actually be effective. And unsurprisingly those who do have experience in technical, specialized fields tend to get poached into the private sector or out of trial (really plea) practice all together, so the knowledge/bullshit gap will still exist and there's no real consistent way to bridge it.

The one trial I sat in on, it was the public defender who hired the expert.

Go figure.

Also the defense is many customers while the prosecution is bulk.