I get this comment from work colleagues too. I am going to walk the Frances for the third time in the summer and my colleagues were asking why on earth I wanted to walk it again and not visit somewhere I haven't been instead.
I simply told them I am really bored of cities as they are so alike as they all have noise, people rushing, congested streets, the same type of shops and er... the ubiquitous kebab places. Going to a quiet beach is really nice for about 3 days and then again, boredom sets in as there's not a lot to do other than read, swim and eat the same type of food all day. I told if I went on holiday to a country I had never been to and was not that interested in going to anyway but would travel there for the sake of simply ticking off yet another country, there would be a high chance I wouldn't really enjoy it but would just spend a fortune on the same type of hotel that's available the world over, the same type of food and to see the same type of places and put on weight etc in the process.
However, I tell them, with the Camino I know I will enjoy the challenge, keep to a small budget even when figuring in a return flight from Asia, meet more amazing people in the shape of fellow pilgrims and locals than I could possibly hope to meet on any other type of holiday, come away from the experience fitter and stronger, not have to worry in the slightest about transport schedules or tickets or any of the other stress involved in most 4 week holidays, enjoy a very different type of cuisine from that which I can get at home, spend time surrounded by more history than I could in most other holidays, live a simple existence that many of us in the West have lost, and most importantly of all reinvigorate my faith and spirit as I walk through ever changing scenery that really cannot be beaten, and visit churches that exude and allow for piety and contemplation.
It really is a no brainer.