In this video it is explored why it is a bad idea to connect solar panels to the load. Solar Panels output is heavily dependent on the impedance of the circuit. The panels have their own internal resistance called characteristic resistance. If the load resistance is close to this resistance, only than the panel will give its optimal output. In reality this is very difficult to achieve.
Therefore an MPPT device is normally connected to a panel to isolate the load resistance from being directly connected to the panel.