Yeah Djinn's right, I have models (not 40k, obviously, they weren't making them at that point) from the early '80s and they're tiny compared to the newer ones. Tom Maier's Elves... horrible. Orcs the size of goblins now, and the first lots of Orks of course... no-one uses RT marines any more, they're smaller than guard... 25mm is more or less 1:72 but the bulk and oversized nature of many of the current ranges make them closer to 1:48 or something. Every time a new special character is released, they seem to make it 'just a little bit bigger' than other models... and whoever asked before, yes, I think some of the guard models are supposed to be about 7' tall.
Curiously, some things that are supposed to be massive - such as terminators, about 9' tall - are modelled a bit small... 1.5" for 9' means that they're... 1:72.
And don't get me started on vehicles...
BTW, "scale creep" is probably the more usual term.
"Well it's Forty-one Thousand Nine Hundred Sixty-nine OK -
Gotta war across the Milky Way - "
Iggius Popiscus and the Stoogii, "41,969"