There is a pretty big problem with alerting a jury about how unreliable eyewitness testimony is: the expense of hiring an expert witness. A defendant could agree with everything a prosecutor asserts except the identity of the perpetrator, but the defendant is going to need someone to testify about eyewitness unreliability.
Anything a lawyer says during opening or closing arguments needs to be supported at some point during the trial; a lawyer cannot just assert during closing arguments that eyewitnesses are extremely unreliable. To allow the jury to hear that information, a lawyer needs a witness, and it has to be an “expert witness.” The Utah Rules of Evidence, which are based on the federal rules, say that any witness testifying on scientific or specialized knowledge, and not on “the witnesses’s perception” (what they personally saw or heard), must be certified as an expert.
Expert witnesses are paid for their time, both in preparing for trial and they day of the trial. If they have to travel, it is normal to pay for travel expenses and food. How much an expert is paid depends a bit on their specialty. Rare specialties and specialties in which a person could be making a pretty good salary outside of court are paid more. Experts on eyewitness unreliability would fall into the “rare” category and are paid accordingly.
This has the compound effect of compromising their integrity in the minds of the jurors. When experts testify, they are routinely asked about the payment for testifying. Many are paid more than $100 an hour, and the jury may conclude the expert will say anything for that much money. Many lawyers decide it is not worth the price to tell the jury, especially if there are other arguments in favor of a not guilty verdict, and other defendants cannot afford the price regardless.