AVR and PIC IO pins are designed to handle loads like PWM controlled servos. Still, bypass capacitors should be used.

Also, until recently, replacing an AVR or PIC was less expensive. Still is, except that the Pi Zero is inexpensive enough to use instead of an AVR or PIC in many applications. And, it gets Perl closer to hardware it's controlling.

Update/addendum:

The Pi is US$25 to US$35 and the micro in it not replaceable except by an expert, so if you damage the micro, you buy another Pi. while there are surface mount AVRs and PICs, you can still get ones you can plug into a socket, so are US$2 to US$5 to replace for many "hobby" projects. So, using an AVR or PIC as a "smart" I/O handler (under the control of a Pi or other, similar device) makes a lot of sense.

The Pi Zero is US$5, so replacing it is almost as inexpensive as replacing an AVR/PIC. So, for some uses, the Pi Zero could be used with out an AVR or PIC as an intermediary.

(Though, because the I/O pins of AVRs and PICs are more robust than those of the Pi's micro, there are still times when adding an AVR or PIC along side the Pi Zero makes sense.)