Unless one is sure of availability of trains all the time, he/ she will not travel to railway station. Nobody would align their flights to suit train timings.
Think of a person traveling from/ to Marathahalli or Koramangala or Bannerghatta road or Hosur road or Peenya or any such area not connected with metro. First he had to get auto/ taxi or bus to railway station, search for airport train PF, get down at airport station and board shuttle. After alighting from flight, je has to get into bus , train, metro and finally bus/ auto to reach his destination!!!.
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more... With so many interchange and Bangalore traffic uncertainty, add train delays, he is sure to get discouraged.
Dedicated PF at YPR, SBC, BNC, KJM and YNK and frequent trains with priority timings only will help.