Yes, they need to be topped up.
Many batteries will have stickers that cover the screw covers on the cells.
Recently it was the case that I had to cut the sticker away to access the screw tops for the cells.
Once the cells were topped up with water, the battery charged much faster and has been working better ever since.
Are you sure acid isn't consumed? There seems to be a lot of horrible corrosion at the battery cables, tray and surrounding area for most cars. This is from acid that can only come from the battery. Plus some batteries are plumbed for venting.
The acid isn't really consumed.
IIRC, the hydrogen gasses escape the battery from heat and discharging cycles (general usage)
The only easy way to top that up is with water (H2O) which has hydrogen in it.