What is the reasoning behind not adding a quote button on each post, or a multiquote system?
Why? Because of Quotards.
What are Quotards?
Quotard - noun. A sub cretinous, mindless, moronic individual who, without caring in the least about who pays the bills for the forum, or for his fellow members, quotes massive strings of text just to add a vacuous comment such as "+1," "QFT," or something similar.
Simply put, people abused the quote button when it was here. So, instead of incessant threatening, cajoling, pleading, and the like, the quote button was removed.