If memory serves, the reason Highlander Burials were 'common' or at least spoken of in parlance was because in Lvl1 tech (which was all the first editions of Battletech had to work with) the Highlander was pretty much the biggest thing with Jump Jets. Thus, the most damage on a Death From Above, since the tonnage factors into damage. And since that damage uses the Punch table (only attacking the arms, torsoes, and head, instead of the whole body) there was a much higher chance of outright killing a mech with a DFA when you've got 85 or 90 tonnes landing on you.
It was just a matter of 'How do I kill this little bugger before it gets behind us, bearing in mind that I dumped my ammo and my arms are gone?', I feel. And then it spiralled out from there.