It comes from the other use of the word Lego to mean a single Lego brick, not just the name of the product in general. If you say "a Lego" to mean a brick, then what do you call multiple bricks? Three Lego? Sounds completely weird to me. So it must be a U.S. vs. British English thing.
A sheep & three sheep
A moose & three moose
A deer & three deer
A martini & really plastered
Oh well, 2 young 2 drink 4 Roses!
Warning!! Handling a Hasselblad can be harmful to your financial well being!
Nothing beats a great piece of glass!
I leave the digital work for the urologists and proctologists.