Why is KNIME so much slower than Python?

We’ve been doing some tests to compare the execution times of nodes in KNIME, (such as Joiner, Row Aggregator, and Row Filter) to equivalent functions in Python (using pandas). We’re using a large dataset with 7 columns and around 20 million rows. We’re finding that the execution times of nodes in KNIME are typically around 100 times longer than the equivalent Python functions.

We were expecting KNIME to be slower than Python, but have been surprised by how much. Can anyone explain why KNIME seems to be so much less efficient than Python? And are there any settings which can be changed which will significantly impact on its speed?