The reason: most deals destroy value for acquirers. The evidence.
And think of DBS’s purchase of Dao Heng, and PosBank. And even Singtel’s purchase of Optus. A dirty secret that the public are not aware of is that value of Optus is less than what SingTel paid for it. https://atans1.wordpress.com/2010/01/15/singtel-lost-at-least-a2-billion-on-optus/