Are we discussing the PEAR installer or everything related to PEAR?
I see no reason to include the PEAR installer by default. Heck, on most distros it's already split out into a separate package.
If I already have to install a package installer (php-pear) to install extensions using pecl, then I see no reason why we can't say "install this other installer instead".
If PEAR works with php7, then great, you can use that as your installer. If not, use pickle, your distro's package manager, or download a precompiled binary.
Exactly. Catch: Many distributions use packaging automation which installs libraries *as pear packages* - as long as there is no way to mimic pear's system-wide installation with composer or as long as the have not retooled to make it look alike.
We're working on it. Pear will not vanish from repos anytime soon - but it should not be part of php proper.