Wal-Mart is currently in the middle of a stock buy-back, which implies that management believes their shares are undervalued. From that perspective, using undervalued shares to purchase an asset would mean using too many shares to do the purchase, resulting in wasted money.

The inverse of this is why companies with "overvalued" stock fund acquisitions with stock.

Walmart doesn't have extremely over valued stock like another dot-com would that would pay with stock

bad yield on cash right now. Interest rates are low, so buying a company with greater ROE than near-zero interest rates is probably good. Unlike many big tech companies, Walmart also has plenty of debt already, their June filing indicated ~$39.4 billion in long-term debt, so adding to that is less appealing than just paying cash. Note: they could do what MSFT did with linkedin and later change their mind and issue debt, since it is very inexpensive to borrow, and Walmart has a good credit rating.

Walmart has money, am I missing something or is there a reason they would not want cash?

You know it won't be unlabelled suitcases filled with cash right?