Why didn't Robert Burns wear a kilt?

Robert Burns was born in 1759. For the first 23 years of his life it was against the law for Scotsmen to wear a kilt (the Dress Act of 1746), unless he was in a Scottish regiment. It was repealed in 1782.

Also, the kilt was the dress of the Scottish Highlander, not the Scottish Lowlander, and Burns was a Lowlander. The kilt only became the national dress of Scotland in the early 19th century, after Burns was dead.