Evidently, it’s because other religions are losing members.
From theScottish Catholic Observer:
The latest figures from the Scottish Household Survey show the number of Catholics in Scotland remaining stable over the last decade, but a drop in the membership of the Church of Scotland and a rise in the number of people claiming no religion. 14 per cent of Scots say they are Catholic in the survey, a statistically insignificant decrease from 15 per cent in 2009. Comparatively, the percentage of people affiliated to the Church of Scotland has declined from 34 to 24 per cent in the past eight years. There has also been a corresponding rise in the number of people saying they have no religion, which no stands at 51 per cent. If these trends continue—with the number of Catholics remaining steady and the Church of Scotland numbers declining at the same rate—there will be more Catholics in Scotland than any other religion by 2024. The research also suggests that the number of people identifying as other Christian and other religion have both remained steady since 2009 at eight per cent and three per cent respectively. The survey echoes other recent findings which show Scotland becoming increasingly non-religious.
Photo: St. Andrews Cathedral, Glasgow/Wikipedia