If you go into low Earth orbit from the Earth's surface, you need to go into an orbital inclination equal to the latitude of your launch site - which is extremely unhelpful if you want to then take that mass anywhere else in the solar system. You also need to circularize your orbit, then later boost that mass from circular orbit to hyperbolic escape orbit - also extremely wasteful.
I still don't see why circularizing the orbit would be wasteful. Circularizing an elliptical orbit at apogee still requires positive delta-v, which will help you on the way to the hyperbolic orbit. Only if you want to circularize at perigee would you need to slow down, which would indeed be extremely wasteful. It's true that you get more energy boost for the delta-v if you do it early rather than late, but I don't know if the ellipticity of the launch orbit is high enough for that difference to qualify as "extremely" wasteful. But maybe it is.
