This occurs for other things across a variety of spheres, but defence barristers are more or less experienced in some of those spheres, and lay people have more or less knowledge in some spheres.
If a police officer tells the jury that they are 100% sure the person they saw with the knife was the defendant, the defence understands how and to what extent they might be able to persuade the jury that the officer is mistaken about this, or how else to undermine this testimony, and they won't accept it if the officer seems to suggest that, since they're sure this was the person with the knife therefore that person stabbed the victim. There are lots of reasons why, even if the jury is convinced their client is lying and had a knife, that doesn't necessarily mean they stabbed the victim.
In contrast when an "IT expert" tells the jury that 100% the only way this database entry would appear is if the defendant stole money, the defence legal team may be unsure how to persuade a jury (since they aren't IT experts) that this might not be so, and they may end up allowing this to go unchallenged even though I would know to ask lots of questions about access, logging, test strategies, and so on.
Or if a medical doctor tells the jury that the only way this baby gets so many broken bones is that her parents were deliberately shaking her because she was crying, and so they're guilty of murder, the lawyer isn't a medic, and neither is the jury. So who is there to tell them that er, actually there can be other causes and the prosecution needs something else?
Light Blue Touchpaper covered some cases where it seems likely what happened is that crap implementations of EMV ("Chip and PIN") were defrauded by crooks who understood where the flaws were and how to exploit them, but the banks went after their customers, telling juries that the machine is infallible and if it says they used a PIN, that must be true, even though the researchers show various ways it might not in fact be true. Further, bank employees will cheerfully tell a jury that there's no way for other employees to discover a customer PIN, even though meanwhile the bank is firing employees it knows did just that. We ultimately cannot entirely insulate the justice system against people who lie under oath. We can only punish them when they get caught.
So, to the extent anything should be done here, you'd want to start with say, not rewarding the people at Post Office Ltd and in the Horizon team who lied about this and tried so hard to prevent justice being done. Two guesses whether the present government chose to do that...