[Retired_for_now]

One really good reason for tabs is bond strength. Unless you're using a gap-filling glue like epoxy, the strength of the glue joint is proportional to the area you are gluing.
So, if you glue two pieces of card edge-to-edge the glued area is very small (card thickness times length of joint). If that's strong enough for the application, go with it as this can be the least visible joint.
If you glue using a joiner strip (butt-block in carpentry/boatbuilding) you have plenty of glue area for a strong connection (strip width time length), but you also produce a hard spot where the card thickness is doubled. The hard spot can be a factor when gluing curved surfaces - but this does produce a smooth seam.
Tabs provide plenty of gluing surface and are capable of joining sharp angles (wing leading edge) but tabs produce that "step" where the parts join. There is also a potential hard spot where the tab has doubled the card thickness. You can hide the step if you crush the seam by squeezing it or by rolling it between a stiff rod and an appropriately shaped backer.

The beauty of modelling in paper/card is that it's your choice. Use the tabs if you like (or design them in) or cut them off and replace with strips if you prefer.

Yogi