yeshivaguy1: To put the record straight, the reason we dont wear a tallis til after marriage, is that the unmarried would stand out and hopefully encourage them to hurry and be mekayem this mitzvah.
Whether this is applicable nowadays is debatable. but minhag avoiseinu beyodainu and we dont change – al titosh toiras imecha. We find the same with sefaik deyoima, that we keep two days of yomtov even though we have calendars, which is mevatel a mitsva deoiraysah of putting on teffilin.
Lesson: dont change a minhag however wrong you think it is. there is always a mekoir.