You may not be a tour person but Pamukkale is much larger than you thing it is. Pamukkale is only name of the region, not the site. The region has 100's of sites, villages, underground cities etc… It would take you whole week to do all the sightseeing. Thats why the tours are highly neat to do this region, especially if you have up to 4 days only.
If you do North and south tours, that will cover the best highlights of region. Walking tour is also highly recommended if you have extra day in Pamukkale, its totally different experience.