1. Majority of people usually buy clothes "off the peg". There is a variety of beautiful clothes nowadays and everyone can find things they like. However, people with non-standard bodies and rich people prefer having clothes specially made. First category has to choose such clothes because standard models and sizes don't fit them as a rule. Talking about rich people, the reason why they choose tailored clothes, is a matter of prestige. They often must show that they are well-off and wealthy.
2. In my opinion, tailored pieces of clothing have only one disadvantage. It's the price. They are usually much more expensive than items produced on a mass scale. However, specially made clothes have great number of advantages. Such items fit better, look nicer and show all advantages of your body and hide all your disadvantages.
3. I would prefer to buy off-the-peg clothes because there is usually a secret in store for you and you never know what clothes you will come across.
4. It depends on my mood. Sometimes it's nice to have a company, to get some advice and hear an opinion of a person you know. But from time to time I prefer shopping alone because I get tired of communication and want to relax.