docs: update intro to readme (#676)

README.md

@@ -9,10 +9,15 @@ _please responsibly disclose_ by contacting us at
 
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-Boundary is a tool for controlling access to networked resources in the
-[SDP](https://en.wikipedia.org/wiki/Software_Defined_Perimeter) model. It is
-designed to be straightforward to understand, highly scalable, and resilient.
-It can run in clouds, on-prem, secure enclaves and more, and does not require
+Boundary provides simple and secure access to hosts and services.
+
+Traditional approaches like SSH bastion hosts or VPNs require distributing and managing 
+credentials, configuring network controls like firewalls, and exposing the private 
+network. Boundary provides a secure way to access hosts and critical systems without 
+having to manage credentials or expose your network, and is entirely open source.
+
+Boundary is designed to be straightforward to understand, highly scalable, and 
+resilient. It can run in clouds, on-prem, secure enclaves and more, and does not require
 an agent to be installed on every end host.
 
 Unlike firewalls, Boundary performs per-access authentication and