Regional channels do have viewership so just bcoz we might not watch them that does not mean they do not have relevance..... These channels show news from smaller towns, villages of the state which they cater to and hence lot many people watch it to know about what is happening in there nearby areas, it is like extension of local news channels which many cable operators provide.
Also DTH / Cable Operators earn carriage fee revenue from these channels which is very important and helps the operator invest more in expanding + improving its service offerings more so when margins in subscription + NCF revenue remain to be low as discounts r given so as to avoid high churn rate in subscriber base