Si-Dog has been taught through school that speaking this way is "slang" and therefore is bad, improper and should not be used. This is purely a recent idea over the last few decades to degrade and erase it.
The like of bairn, wee, bonnie are not slang but good standard words that have been used for many hundreds of years around Scotland and still commonly used today.
There's also several different dialects (and even more accents) in Scotland where words might be pronounced differently or use different words altogether.
For example the word "ken" in Scots is the equivalent of "to know" or "to inform". It comes from older Germanic languages ("kennen" still appears in Dutch and German).
Ken might be said as Sht = kjen, Fif = kain, Ang = kin, Abd = keen, and so on around different parts Scotland. They don't apparently use the word in Glasgow at all.
Same applies to many other words that can be said differently around Scotland, like of "laddie" (mentioned by someone else on here) that can be lathie, luddie, lawdae and so on elsewhere.
More to the east, north and islands is it the strongest or still properly spoken. The like of Shetland islands is the purist due to it being remote. Their dialect also has a lot of Norwegian influences in it (see link) and is taught in schools there.
Of course, there's also Gaelic too which is something entirely different (not Germanic) and used more in the Highlands. It has nothing to do with any of this.