An answer someone else on the forum gave me is that it has to do with some legal differences between Scotland and England. I've expanded on the basic answers I was given to explain em more, but I'm not sure if the basic "answer" is right or not.
Firstly, in Scotland only the Crown Office/Procurator Fiscal can begin criminal proceedings.
In England, "Private" prosecutions are permitted, meaning they can be brought by other people. The CAA, RSPCA, the Railway Companies, as well as the DPP can prosecute in England.
The result is if you're in court on criminal charges in Scotland it always is the Fiscals you'll be facing - meaning that Scotrail would be dependent on the Fiscal's deciding that the case was in the public interest and deciding it was worth their time to persue. Bit hard to back up your threats of prosecution when you can't do it yourself.
In Scotland, for a criminal case to succeed each "Essential fact" is required to be proven with at least two pieces of evidence. This is called "Corroboration".
The SNP proposed getting rid of this rule, but all but about 2 judges in all of Scotland were opposed to such a change, fearing that it would result in more "Risky/umerited" prosecutions being brought (The SNP liked the idea it as it makes it easier to prosecute Sexual assaults).