Why, because trading goods was the only way to get something you wanted from another place. Unless a shop keeper or a barterer has the item you wish for, trade was the only other option you have to get your item. In towns, the most trading often took place. Travelers stopped to rest in towns and may have the item you are looking for. So if you lived in the Renaissance period where would you want to live if you where a Trader? Power, the more powerful you are can make you become a great successor. If you had rower you could have it all.
However Feudal Lords with power in numbers, such as armies and other things, where becoming less needed in the Renaissance period. Now, since war was over, people now focused on wealth. Soon, wealthy merchants started a new class of power and became the powerful ones in the Renaissance period. Wealth was power. Status, status is your level in achievements and other things. If you where in a guild you could raise your rank by your status. If you where higher in rank in the guild you loud have a better over all status because people could come to you for answers.
Guilds where starting to dominate the social life of everyone. Status also can lead to power. Trade and commerce was becoming the thing that would take over the Renaissance. In a good way though. Society, helping others and trading goods across borders then trading with the locals of your home town. Power, no more huge armies, Just wealthy merchants. Status, work your way up, and maybe even Join a guild. That was trade and commerce of the Renaissance period.