Odd position in the pokedex

[The name master]

In most pokedexes, legendary pokemon are listed last.

Example

In gen 1, mewtwo and mew are last.

However, there're some non legendary pokemon that appear amongst the legendarys.

In gen 1 dratini and it's evolutions appears between moltres and mewtwo. In gen 2, larvitar and it's evolutions appear between Suicune and lugia. Why?

[The Hooded Trainer]

I believe it's because the developers had no idea what they were doing and were pretty much just winging it for the first few gens.

[Captain Jigglypuff]

The spots where the Dratini and Larvitar lines are probably placed there to signify that they are pseudo Legendaries and that they evolve at higher levels than most Pokemon. Gen 4 is the exception of course.