Plus, with SaaS, there is another dimension. There is also the requirement to protect user data from each other, not just from external sources. Check out Rudder, who recently managed to show users each others Bank Account info. The problem is much more complex than it seems.
If you use Twitter, you will notice that in the last month, it has been affected by a huge amount of spam. It’s not just overhead, no one wants to continue using an application that has unnecessary data and inconvenience.
Web Apps: the here and now