Land snails are sluggish and therefore they stand almost invariably for too slow.
Sea snails seem to have a different vocabulary. They may radiate luxury, or stand for the Sea.
As with other animals, we also have some examples where we have no clue why a Gastropod was choosen.
In today's fast world snails are considered way too cautious in their actions. That is why the animal usually stands for something that should be avoided, or at least can be done much faster: f.e. long waiting times when applying for a loan (1, 2).
This is one of the very few advertisements where land snails do not stand for something that is slow and must be avoided. The snails simply represent the everyday world which is contrasted with the F1 world which is moving much faster.
In the following ad (6) also, the snail's sluggishness is presented as a fact, not as something that is bad and could be better. The device of No. 6 detects vibrations on machines that run at only six revolutions per minute. The animal plays the role of equipment suffering from vibrations. There's also that hint of mild humor that we love to see in commercials.
I am not sure that our next example (8) really is an advertisement. It is a full spread from the inflight catalogue of Alitalia. It may very well be the opening page of the section with jewelry and watches and not an advert for a specific (kind of) items. However, the association of a sea snail with luxury goods is remarkable. Just like when Ants were chosen for jewelry and watches, we have no clear understanding of the reasoning behind this connection.
Only a reader, who knows that the commended device was a heavy-duty printer which in its "M"-version could work with a Macintosh and other PostScript sources, would maybe see the reason of the language statement. I am open to suggestions about the remaining elements of the advertisement.