Flipside: drastically changing a brand's sizing standards has repeatedly driven me away from long-time favourites.

This happened to me several times from the 1990s through the aughts. Literally between one shopping session and the next, the same style of clothes (tops, bottoms) which had fit perfectly no longer did, resulting both in a set of returns (of clothing) and non-returns (of myself, for future purchases) to those stores. As someone who generally dislikes the shopping experience, additional and insurmountable frictions such as these are absolutely fatal.

More recently (as I've just commented) it's the widespread adoption of stretch fabrics in non-athletic wear. I may want stretch in some of my workout clothes. I don't want it in my street clothing.