Surely you are right, but whales are mostly investores.

Because most of the users do post quality post but dont get rewards on their post which make them feel that they are wasting their time

That is happening also to whales when they post, lack of economic efficiency. A lot work, few income.
Interest rates as an investor, on the other hand, are reasonable.

Someone posting on Steem is an idealist, maybe a hobby or just fun.
With HF 21 just arrived voting on a large scale has become significantly more economical, so hopefully there will be more vote activity bit by bit.