Some high BW scopes have dedicated 50 Ohms inputs. Beyond some 500 MHz the normal 1 M|| 20 pF input is no longer high impedance, because of the capacitance. In addition cable reflections get more and more important, so that passive probes are about limited to some 300-500 MHz.
A dedicated 50 Ohms input can be lower noise than a high impedance input and is also easier to build for high BW.
So some scopes made for high frequency skip on the high impedance input. If high impedance is needed, one adds an active probe.
Instead of an expensive active probe one may as well by a cheap 200 MHz DSO instead as an alternative instrument.