There is something to be said about being face to face, eye to eye with your client. Some people just don’t like that. But my best client’s are the ones I’ve had for years that have become friends because we meet for a beer or coffee and discuss their vision, plans and goals - not just the job.
Listening is a skillset. According to “them” (some scientists somewhere) only about 40% of what is spoken is actually understood by the listener. If you go through a site, you are compounding that problem (- think of the kids game “telephone”). I spent years in advertising. I spent years in mediation. From each of these disciplines I learned specific communicative techniques. Google “active listening” as a starting point.
Additionally, sites that get you work don’t want you taking “their” clients. So they are setup to keep the minimum contact between you and the client as possible.
Finally, there is a difference between a customer and a client (imo). Customers are on those sites to find someone for a job. These sorts of customers almost never turn into long term trusted clients because they are woking piecemeal. You want to build a client base that trust you and comes back to you because you paid attention to them, executed the job, and provided “personalized” care.