From Bill Bryson's The Mother Tongue:
I can think of two very good reasons for not splitting an infinitive.
1. Because you feel that the rules of English ought to conform to the grammatical precepts of a language that died a thousand years ago.
2. Because you wish to cling to a pointless affectation of usage that is without the support of any recognized authority of the last 200 years, even at the cost of composing sentences that are ambiguous, inelegant, and patently contorted.