Thanks to the PriceWaterhouseCoopers book Five Frogs On A Log for this one - the ten most common stated objectives of CEOs looking to make an acquisition:
Access to new markets
Growth in market share
Access to new products
Redirection of operating expenses
Enhanced reputation
Access to distribution channels
Access to additional management or technical talent
Reduction in number of competitors.
Reduction in distribution costs
Access to new brands.

It misses out one reason - personal aggrandisement.
And does the book say how many acquisitions actually achieve the CEOs' objective?