Re phenolic...
My understanding is that it was an early generation plastic for mass production. Commonly called 'bakelite', it is a thermoset type of plastic. That is to say, heat is required for it to become hard and retain its shape. It does, indeed, result in a brittle product, though...testiment to the broken and chipped products using this material.
It was replaced by the more commonplace generations of materials, known generically as thermoplastics, in use to this day. Thermoplastics require heat (melting) in order to flow into the die under pressure, but do not harden completely until they cool.
Looking at it another way....recycling...thermosets are all done once they've been processed into a die. Bad part?...to the dumpster. Thermoplastics can be re-heated and re-used. Bad part?...grind it up into small pellets (as originally provided by the industry), re-heat it, and shoot it into your mold, etc..
And, depending on the type of thermoplastic, VERY sturdy to abuse in comparison to the thermosets.
There's a lot more to the comparisons....but that's the general idea.
FWIW...always.
KD