Spodman,
Block altitudes can be utilized in a variety of circumstances and is quite commonly used. Below are a few examples of when I've used Block Altitudes:
Air carrier and air taxi aircraft doing IFR training (stalls, steep turns, etc.).
NASA aircraft doing icing test and wanting to stay within icing conditions.
Military aircraft in large formation flights or multiple flights.
Or other aircraft wanting to stay out of the clouds.
Mike R
NATCA FWA