When did Lego stop putting small catalogs into boxes?
To be fair, it is hard to tell and depending on definition you may even tell TLG has never stopped doing so. But it depends on the series.
Bricklink has a lot of catalogs in their item data base. Single leaflet catalogs are called &quot;Mini&quot; and small booklet ones are called &quot;Medium&quot;. Catalogs you can find in store are called &quot;Large&quot;.
While Bricklink's database can be considered the largest in terms of catalogs they have, for some reason they didn't record if any of these catalogs come in sets. So it is hard to say when/if did TLG stop including Mini and Medium catalogs. Looking at the data recorded in Bricklink I would assume 1999-2001 are the years when TLG stopped putting &quot;Medium&quot; catalogs into System/City/Technic sets. It also depends which series you are interested in, since Duplo kept getting their &quot;Medium&quot; catalogs for much longer. However you can also find that some of recently introduced Dots sets may have had catalog of &quot;Mini&quot; type in their 2020 range.