Why are Erlenmeyer flasks shaped the way they are?
Imagine a time when magnetic stirrers were unknown. You, or your lab assistant, would mix solutions in suitable glassware, shake manually, put it aside and then observe a change.

An Erlenmeyer flask is much more suitable than a simple beaker 


the flat bottom gives it a stable stand on the bench
the narrrow neck allows to hold and shake a large flask with one hand
the conical shape prevents spills when the flask is shaken circularly