Why isn't a flip chip an industry standard that chip designs should use ?

[94d33m]

Considering that flip chip has bond pads below substrate so we can route power from bottom side and do routing on top side, isnt it so much better?
What are the issues ?

 

[FvM]

Considering that flip chip has bond pads below substrate

That's not the commonly understood meaning of flip chip technologie, see https://en.wikipedia.org/wiki/Flip_chip

 

[dick_freebird]

Bare dice can be and are attached flip-chip style but outside of modules many IC technologies are not robust without a package. Wire bond can use standard package s / leadframes as the wire bond is "any to any" (within geometric reason) but flip chip needs the die and the "target" to dead match pad locations.

Issues with thermal budget on assembly can also argue against solder ball type attach