Must I accept a new position after interviewing?

I speak with professionals daily, recruiting them for positions with their competitors.   The most frequent objection  that I encounter is that "I am happy."  When asked what their current firm provides, it usually includes non-specific reasons about nice people, corporate culture, being comfortable etc.  Basically, folks are telling me that it is easier not to have to consider an alternative. 

This always brings me to several questions.  Sometimes I ask them, but usually not as people seem to take offense.  Is this the happiest that you will ever be?  How do you know that another firm may not value your talent enough to provide everything that makes you happy with your current firm and more? 

There are numerous reasons to agree to interviews.  The main reason being is that it puts you in a position to fully understand what a competitor may offer rather than assume that your current firm is up to date on technology, has the ability to attract the most interesting projects, or is valuing your skills and supporting your goals as well as a competitor may.  In addition, expanding your professional network is always beneficial to enhance learning and perhaps create teaming opportunities. 

To thoroughly analyze a new company/position, several meetings will probably be necessary.  You are empowered to ask questions and research the firm at various stages.  After doing so, you have the choice to accept an offer if presented, propose different terms like compensation, roles, responsibilities etc., or decline and remain with your firm if the company presenting the offer doesn't provide compelling reasons for you to make a change.  You risk nothing by engaging in this process and may never know what riches (cash, opportunities, relationships) that you forego by being complacent.