Unlike modern lighthouses, which are used as warnings, ancient towers were used as entrance markers to ports. They were built because they had a very important job to do. Their task was to guide ships safely into a port. We have much in common with lighthouses.
I also know for a fact that you too were created on purpose with a purpose and plan to fulfill. We were created to share the gospel light to give the lost directions to enter into eternal life with the giver of life. Are we busy doing our created task?
Ephesians 2:10 (ESV)
10 For we are his workmanship, created in Christ Jesus for good works, which God prepared beforehand, that we should walk in them.