How Importance works
For the whole network, content and interactions with it (such as upvotes or downvotes) are merely the tip of the iceberg. Importance measures the value a given account creates for the whole network. This value adds up to the overall value of the network, attracting newcomers, which may in turn affect the network's external presence or token price,
for example. Stake is still important, because those people holding it did something valuable and received their stake in return. For example, offered some kind of service, sold goods, received dynamic emission, claimed their block producer's reward.
Transfer activity is also valuable. Look at small margin shops - those ones have huge traffic and turnover, serving lots of customers, contributing to the development of any economy, including a digital one. Those actors rarely have large stake at their disposal, but the amount of incoming transfers maybe tremendous.
Social activity is the next level of interaction, as it provides us with an opportunity to reward anyone without losing something in return, on the contrary to tipping and donating. Your upvote or any other type of social action contributes to other person's social activity index, that may in turn be monetized via dynamic emission and converted into stake.
All three parts are Important, and the contribution of each one tho the final Importance index can be voted upon by the delegates. Making the system activity-focused would make it overly volatile (as you can see for yourself by looking at our social activity date daily fluctuations) and prone to easy manipulation and abuse.
this is shared by @spirinspirin as a comment in a post related to how importance works. don't want to go down without reaching community that's why sharing here (whole credit goes to him)