I cannot dream of a reason why they would do this… is it the program they use? Is it for legal reasons? Who knows?
Here’s an example:
It’s not just the apostrophe, it’s the next letter too.
Theory: if a standard upright apostrophe were used, there wouldn’t be a problem. If, however, the person had composed the thing using Microsoft Word, the program would be using “smart” single quotes as apostrophes that lean to the left or right, which have a non-standard ASCII code. The lyrics server is a bit primitive, and thinks that the non-standard ASCII is introducing a double-byte character (as used in ‘foreign’ scripts such as Japanese). In turn, it doesn’t actually use double-byte characters, so just gives a default ‘?’.