Some can be incredibly useful. Not really necessary though.

For example my ninja has a macro
/ac shade walker <2> which will always put it on the tank so they get the enmity boost.

Bard you can macro flaming arrow to <t> so it will always centre it around your current target. Without having to manually place it.

My scholar has summon macros that swap pet commands. So when I summon eos L2 square is whispering dawn. When I summon serene l2 square is changed to fey wind for example.

Then simple macros like /target <f> or <attack1> can be really helpful.

Or can't remember who told me this. But macroing /levelsync on to your mount. Is really nice for fates.