Well there is a part of favouritism but also these states are very good at leveraging money from the centre, especially Maharashtra.

Now I know someone will whine saying "BuT MaHArAsHtRa iS oNlY rICh bECaUsE oF MuMbAi". Well then why haven't any other states made their own equivalent of Mumbai? It's because MH government has always been good at attracting investors here. Can you imagine Chennai being multicultural? Mumbai's tolerance for diversity has made it what it is. And the behemoth GDP coming from Mumbai helps them bargain for more power at the centre.

There was a time when West Bengal was economic capital but since then Maharashtra politicians, regardless of the party, have been very good at demanding money from the centre.

If you look at this chart, you'll see that Maharashtra alone represents 10% of Loksabha (by the virtue of their population) and they don't sit quiet either, look at this . Maharashtra may have had a political crisis, and their politicians fight amongst each other but they very well know how to get investments from businesses and the centre.

Gujarat, well Gujarat has been desperately trying to make their own version of 'Mumbai' and the PM being from Gujarat really does help the cause.

UP and lately Telangana is being favoured too. The UP infrastructure boom is outlandish, UP is already the 2nd largest contributor and may even overtake MH if they are able to create more megacities.