Why can't you export the static site and let me host it myself?
1) you still need to have and maintain secure the WordPress Installation somewhere. With HardyPress WP can be paused and restored when needed with a click.
2) you have to download the static version and upload it somewhere else manually (your client certainly can't do it on their own). HardyPress does it with a click.
3) contact forms and search will stop working. With HardyPress, if you use CF7, everything will work seemlessy.
To solve the problems above HaryPress needs to hosts your WP installation.
How could this be achieve without hosting files and DB?