The reason Stocks are split is to make the stock affordable which thereby helps increase liquidity and help discover the true value of the company. While the company does this in it’s own interest and in the interest of it’s shareholders, it’s not compulsory for them to do it. I can’t think of any specific reason why the stocks aren’t split.
BTW, do you know that the price of Berskshire Hathway on today’s date is a whopping 2,17,000 $ https://www.google.com/finance?cid=4376
Mainly because of the management’s decision to:
To keep the voting pattern unchanged
To keep the speculators away from wheeling and dealing its shares like a lottery ticket.
they will split when ther management decide to split