How could "pet " or "smoke" affect new unopened Lego set?

[ks6349]

On ebay, many sellers claim that they are from pet and smoke free home while they are selling brand new and sealed Lego sets.

How could pet or smoke affect brand new and sealed sets? Just wondering

[Terrasher]

Dog & cats can damage boxes if they get near them (clawing, biting).

Other than the smoke smell (and maybe discoloration? I'm really not sure), I don't know how smoke can affect an unopened LEGO set.

[splatman]

The bricks themselves may be unaffected, but a smoke-smelling box will be turned down by anyone shopping for a MISB set.

[MAB]

It is mainly useful for parts sellers.

Some people have an allergy to animal hair, hence some stores state that they do or do not have pets.

Smoke can cause bricks to smell, whether it is caused by the smoker touching the parts or by them being in storage in a house where the seller smokes.

 

[AmperZand]

10 hours ago, MAB said:

 

Smoke can cause bricks to smell, whether it is caused by the smoker touching the parts or by them being in storage in a house where the seller smokes.

 

Indeed. Cigarette smoke is not too bad. If parts are left to air out, the stink disappears in a few weeks. Vaping smoke, on the hand, lingers for months. One or more of the postal workers in my area vape leaving parts I have ordered on BrickLink stinking of cherries. It drives me mad ? 

[Littleworlds]

Another thing I can think of with pets is that there is the chance of peeing, causing a smell that can be hard to get away again. As for smoking, I bought a batch of Lego (individual pieces, not a whole set) from a bricklink-seller who seems to be a smoker. The bags smelled a bit, the bricks themselves got a quick rince with dishwashing liquid and were completely fine afterwards.

[Jacob Nion]

I would say that it's mainly a standard ebay phrase somebody at some point started and now everyone uses, even if it's irrelevant. 

For furniture for example it's certainly an important point. And casual evay sellers are no expert Lego sellers. And so they adapted it.