I use Contacts app as a contact book of people I both know and people I am interested in.
I use this workflow to quickly search through all my contacts. I add tags (i.e. the name of event we met at or person's skills/interests) to make both the searching and remembering who the person is or what he does easier.
del as part of the name contacts that are temporary. I then cleanup these contacts when they are no longer needed. i.e. You need to add person to Contacts just to send someone a WhatsApp message. Or agency contact for a place I rent.