in water fall model one disadvantae is their i.e in this 
model verfication & validation r not done and also in the 
middle if any req r change by customer then it is not 
possible in wfm but all of the disadvantages r correct 
address properly in v-model so now companies use v-model.

Pavan,

Please understnad the question once again, you mean there 
in no drawbacks in V - model!!!. No software companies 
using the model which doesn't have V& V method. As quality 
perpective, V&V is core for testing.

The question is why water fall model is used everywhere? 
But the answers support V model. Try to analyze the 
question. I think the question is wrong. It must be V model 
in place of Water fall model.

Then the above answers will be correct

First of all where do you get your statistic about water 
fall? That is incorrect.
A lot of company are using either agile or v & v.

In water fall requirements are seal while in v&v you can 
change req. as you which. This is to customer favour.
Testing can start during requirement gathering in v & v. 
While in waterfall, you got to wait for the FRd to be 
approved.This just a few.