Every subclass except 2 has a feature that either a) scales their weapon damage, or b) enhances their (automatically scaling) cantrip damage.
It is intended that you will have access to that scaling damage. Spending your turn making a 1d8+3 attack at level 17 just doesn't really do much.
The two subclasses that lack that feature (for some reason) are the poor land druid, and the lore bard. The lore bard, however, has the ability to approximate either route. They can take eldritch blast or firebolt for the best ranged cantrip damage (even without the +ability mod some casters get, those spells are powerful enough to meet the goal), or they can take greenflame blade (or booming blade) for a scaling melee attack. (Or they could take both.)
The one point I'm making is that if you don't take greenflame/booming blade your character will not be at an expected level of performance for melee once you get into the mid-levels. So if you want to actually use a weapon, you should take greenflame/booming blade. If you plan to be using ranged attack cantrips, and your weapon is just for show and opportunity attacks, then you won't need it.
(The sad part for the poor land druid is that they have to take a feat to get it, which requires a more optional rule, and in some games (like mine) requires some story content, while the bard can take it as a built-in class feature. Ie, a "regular" druid can't even have it. We need a new druid cantrip that does basically the same sort of thing.)