Here's why they were chosen:
* Blood Protection: Lily Potter's sacrifice, coupled with the fact that she was a powerful witch, left Harry with a powerful magical protection that would only hold while he lived with a blood relative. The Dursleys, being Harry's aunt and uncle (his mother's sister and brother-in-law), were the only family he had left.
* Ignorance: The Dursleys were "normal" and completely ignorant of the wizarding world. This ensured they wouldn't be able to intentionally break the protection, even if they wanted to.
* Petunia's Envy: While Petunia initially wanted to be a witch, she was rejected from Hogwarts and likely developed a bitter envy towards her sister. Her desire to distance herself from magic also contributed to her decision to raise Harry in a strictly "normal" environment.
So, the Dursleys were chosen for Harry's protection, not out of love, but rather out of a twisted set of circumstances that played into the magical world's need to protect Harry from Voldemort.