The rules of evidence prevent many prior bad acts evidence from being admitted or asked about. The jurors are always going to think the defendant had something to hide if he doesn’t testify. Although I’m not a criminal attorney (only one criminal trial in my career), I’ve tried a few dozen cases — hundreds of jurors — and have a pretty good feel for how they behave.
My fiance happens to be a criminal defense attorney, before that, she was an ADA. One of the things she talked to me about, was what a mistake it is, for defense lawyers to put their clients on the stand (guilty or innocent).
There is also the whole issue with making the defendant look like a liar, by tripping him/her up on details when you hit them rapid fire, to the point, where you confuse them, while the jury thinks the defendant is trying to hide something.
There are tons of ways to make someone look bad on the stand, she has made it appear that cops are lying or hiding something, taken apart witnesses, and shredded "experts". A prosecutor that does that to a defendant, has pretty much won their case.
You also get into the 5th amendment side, the way she sees it, once someone invokes their 5th amendment, the jury takes it or acts like its a confession of wrong doing (even though they are not supposed to do so), and the whole point of anything is now wasted, and your guy looks guilty as sin, with nothing to show for it.
Sidenote: She actually once won a case, where her client attacked a lesbian couple during a gay pride parade, with hundreds of witnesses, I still can't believe she pulled that off.......lol