Why does kmail insist on having ldap available?

[Peter Humphrey]

I've just noticed my Gentoo system updating openldap and looked into what 
needed it. All dependencies were conditional except for kldap, which requires 
it. Then I found that six KDE apps insist on kdap and thus openldap.

My question: why is ldap not optional? What proportion of user installations 
actually use it?

-- 
Gentoo testing system
gcc 9.1.0, sys-kernel/gentoo-sources 5.2.2
QT 5.12.4, KDE frameworks 5.60.0, KDE plasma 5.16.3
KDE apps 19.04.3 incl KMail 19.04.3 (5.11.3), akonadi 19.04.3
dev-db/mariadb-10.3.16
x11-drivers/xf86-video-amdgpu 19.0.0
dev-libs/amdgpu-pro-opencl 18.20.684755