Dear Luis,  

I really don't know why. One thing is to encourage a young person to have normal friendships, and quite another to encourage dating. Dating is good and necessary if you are called to marriage since you need to get to know better this or that girl that you are attracted to, to see if she is "the one". But does it make sense if you think you have a vocation? 

Some people seem to think that dating will "get it out of your system", and that if you date before following a vocation you will be less tempted afterwards, less curious, less attracted, and hence more mature in your vocation. Remember, by dating we are not talking about having friends who are girls, enjoying their company, and doing things together with a mixed group of friends...; we are talking about a couple spending time together, looking for each other, tacitly or overtly committing themselves not to go out with someone else, etc.... 

The best preparation for a vocation is to grow in love, but in love of God, and learn to make choices based on what we think God is asking of us. If we are normal, even if you have a vocation, dating at some stage and with some person will lead to deep emotional attachment. So what do you do then? Why play around with the possibility?  

This applies to the healthiest and purest of dating relationships, but with our human weakness, the pressures of friends, and so much moral laxity around, don't worse situations often develop, even for those with the best of intentions? We have to live in reality and choose the safest path.  

So, if you are discerning a vocation, it is time to test and see if you can maturely live the type of love for God that the vocation implies, and freely accept to keep your heart exclusively for him.  

God bless.