Why would a recruitment agent want a face to face interview?

I would say this is a good sign. Remember that your recruitment agent has to deal with hundreds of candidates. If he is investing the time to get to know you in person, you must already have done some things right.

Now why would he do this, there are several possible reasons. For example:

• He wants to test your soft skills.
• He wants to explore what your long term career goals are, to maybe get better offers to you in the future.
• If he recommends you to an employer, he wants to be sure you will fit there, socially.
• He has had bad experiences in the past, with forged documentation, identity theft etc.
• He wants to build a connection with you, as he knows good IT staff is always in high demand.
• He just prefers to do business in a more personal style.

I'd recommend to always go for the personal meeting if possible. Who knows what future options you'll open up if you make a personal impression. Right now you are just a file to them!