I don't know about MCI much but FYI Khammam has 3 platforms not just 2...
Second, for the whole Khammam district.(new and old) ....Only Major railway station is KMT where as MCI being in close proximity with RDM and BPA may be a reason for not having all trans stop at MCI which stops at RDM and losing out most trains to RDM...
There can be other reasons as well..But I don't think having more platforms will give more trains .....