Curious. I always prefer 100% cotton, and nothing ever shrinks noticeably. I thought shrinking clothes were a historical oddity from my childhood, honestly.

A couple things that might make the difference:

  - Conference swag shirts might be a lower quality/more shrinkable weave? I don't buy anything special.
  - I wash on medium or cold temp, never hot (except full loads of towels), and dry on medium. Everything always comes clean.

Ime, some shrinkage is inevitably if you wash with reasonably hot temperatures. Reasonable ~ following the washing instructions. Most mid to high end tshirts are pre-shrunk however which helps a lot, low end shirts (maybe some conference swag?) can skip this step for cost reasons.