Does it necessary to collect lease signer's drivers license info?

[Wendy Home]

I rent my house to a couple, after tenants signed the lease but before I hand over the keys to tenants. I asked the signers to provide a copy of their drivers' licenses to me. They asked me to provide them a solid rationale reason why this is required. As a landlord, I need to keep a copy of their drivers' license on file, what should I tell them about the reason to collect the drivers' license?