Eight legs under one sofa is not decoration. It is arithmetic.
A long seat rail carrying three people bends in the middle - not visibly, but enough over years to loosen the joints at each end and put a permanent sag into the seat. The traditional cure is a deeper rail, which raises the sofa's apron and spoils its proportion. The other cure is more legs.
So the intermediate legs on this frame are not applied to the front for show; each one is jointed into the seat rail directly above it and carries load down to the floor, dividing the span into short sections that cannot bend. That is why they are placed at the points they are, rather than spaced evenly for appearance.
The carved apron is then set out around those fixed positions, with its densest passages falling over each leg. Which means the ornament follows the structure rather than the structure being bent to suit the ornament - and both end up looking right, because the eye expects support where it sees weight.