Hi Kim
It means the pre-1855 baptism, marriage and burial records in Scotland are harder to find for the non-conformists and indeed may often not be found at all; it depends on what religion they may have been and how the clerks in the place of worship they attended (or affiliated to) kept records. You will find that pre-1855 records in some shires or towns are more sparse than in others, and that some shires or towns were more likely to have a higher level of 'non conformist' inhabitants.
With the Established Church (conformist) the records were kept at the Parish in which the event occurred, and the Parish was established by set boundaries and every Parish had it's established place of Worship. Not always the case with other denominations - Weslyan, Methodist, Baptist, Quaker, Catholic, Dissenters etc. Even in the established Church, not all Parish records survived or were fully kept Pre-1855..
Scottish records are excellent generally (not in the least, for me anyway, because of the recording of the mother's maiden name on baptisms and burials, and post-1855 naming both parents of an individual at marriage or death).
So unfortunately for us searching centuries later, the lack of a marriage record between an Angus CRAWFORD and a Mary COLVILLE isn't odd at all.
http://www.genuki.org.uk/big/sct/RFW/Abbey/https://familysearch.org/learn/wiki/en/Scotland_Church_Recordshttp://www.genuki.org.uk/cgi-bin/churches?CCC=RFW,GR=NS485639,DIST=3,PLACE=AbbeyCheers
AMBLY
