Scripting features are in development - just read the forums you will find info on it - a good start is http://www.gamesas.com/index.php?/topic/1168606-wizbain-projects/. I was waiting for further development before I go back and revise sections of this thread (hence warnings at the top).
There are already BAIN wizards for scripted installs - not a lot but they exist. Check http://www.tesnexus.com/downloads/file.php?id=19628 out. Also as of the last Bash revision BAIN does handle OBSE plugins.
As for why there are a lot of omods is because BAIN has only been around for not even half as long as OBMM and hence most of the initial modding rush utilized that format. Things are changing as the modding scene gets more complex and users more sophisticated.
You are of course welcome to your opinion of things, but I will point out a flaw in your reasoning. Oblivion is not a plug and play game. OBMM gives the false impression that this is so. But what is convenient to use about OBMM has to do with mod makers take the time to package it with OBMM to make it seem a simple thing but it is not and OBMM hides much. So much in fact that until you make the leap to BAIN you don't know what your missing.
I break it down like this. If you can successfully mod your game you are a modder (even if just applying the mods others make). If you make mods - a mod maker. If you rely on others to mod your game and hold your hand through scripted installs then the label mod user applies. BAIN is for modders - those that look under the hood and take responsibility for their own installs and load order.
It is not a popularity contest either. Utility is the goal with BAIN not ease.