Courts are generally heavily booked, trials take forever, it's a perennial news issue that courts are underfunded (this seems to be a major factor behind the incredibly nasty and abusive rise in 'offender-funded' court systems & treating traffic violations & civil asset seizures as normal funding sources to be maximized) and I've seen estimates that as much as 90%+ of all cases resolve as plea bargains. There's no way the court system could handle a sudden 10-20x increase in workload, which is what would happen if prosecutors stopped settling for somewhat reasonable plea bargains and tried to throw the book at suspects who would then have little choice but to take it to trial.

(I recall reading about an attempt to organize defendants in one US court district to agree to not plea bargain, overloading the system so badly that most of the cases would have to be dropped; but I don't recall what happened and can't seem to refind it. I'm guessing it didn't work out, given that this is almost literally the prisoner's dilemma.)