Yes ur write by using the automation tools we can do the 
project fast but still we use manual because the automation 
tools are too cost and all the companies cannot affort such 
huge amount for the tools so most of the companies use 
manual only.

I would like to add few more perspective to the above 
answer...See,automation tools never think like humans 
brain.It is not like just connect the application to the 
tool and get the result.We have to create many scenarios 
which can be used as the input to this tools.And we can 
create scenarios using manual testing techniques.
Secondly,it is not feasible to automate each and every 
application,automation best helps in regression 
testing/retesting.
Automation tools needs experienced/trained personnels,which 
in turn increases testing budget.
Thats why most of the companies go for manual testing 
rather than automation testing.

hi
   ya automation tools are too fast than a human brain but 
we cannot use automation in every part of testing.the test 
cases which are reusable needs to be automated bcoz 
repetition is sometimes a tedious job.so at that time we go 
for automation.at the same time as the tools are very 
expensive most of the companies may not effort to buy 
them.

reason for using manuak testin

1)Cost effective
2)automation cant be used where requirements changes 
frequently.
3)automation can be used only when rquirements has gone 
many refinements and changes comes to almost minimum 
otherwise no use of automating a frequent requirement 
changing product.
4)for example while the software has got some new additions 
then we can test the already written codes by automation 
(regression testing) and new codes by manual testing!!!

Even though automation of testing is faster than manual
testing,those tools can be used for the pre-specified test
cases only,So in s/w more changes can takes place due to the
change in requirements.So Before release only automation can
be done,until then irrespective of the com/cost of the
project manual testing only carried out..