This can be a complicated thing since you are going for leisure and not business, right? Usually Surat Jalan or also known as SKLJ is usually good for only 3 months and is used for people who are traveling to certain regions of the country for certain purposes (usually business/technical). In my 26 years of traveling across the archipelago, I have never had to show it to any authority, although it is usually the up to the Human Resource department of companies to obtain it for their employees.
IMHO, it is another money making opportunity, since a valid passport and visa/KITAS should suffice during travels in country. Sometimes I think it is just extra lunch money for the HR manager to take care of, such since large companies are paying for it.
Again, don't take my word as I am just giving you an example from experience.