But without such frictions, financial markets have little reason to exist. For example, with complete markets (and if we ignore taxes), we know that whether a corporation finances itself by debt or equity is irrelevant (the Modigliani-Miller theorem).
The blossoming of work on asymmetric information and principal-agent theory, led by Nobel laureates Joseph Stiglitz and George Akerlof and with contributions from many other researchers, gave economists the tools to think about the central role of financial markets in the real economy.