I didn't watch. I had a bike stolen with a locked gate and there was nothing I could do to stop a thief. They can jump my fence. I am not home a lot. So, I learned not to leave anything of value ON my porch.
There is nothing coming to me by mail that anyone else would want. I don't get money in the mail.
There have been instances in Britain of goods left by couriers on front door-steps when unable to raise an answer, being stolen.
Unfortunately a lot of deliveries now are by such companies, and they have no, or only weak, methods for holding parcels not directly deliverable to private homes. Most such firms were established for business customers, so their sorting-offices can be few and far between.
If you use Royal Mail, the parcel would normally be taken back to the local sorting-office, with a card left giving the telephone-number and web address for you to re-arrange re-delivery or you to collect from Post office or sorting-office; on production of identity. It is a secure system, and in my experience, it works well.
Some shops now belong to a network by which courier deliveries are to it for your collection - for a fee added to the original sale and delivery cost.