Some people tend to avoid Software as a Service due to the fear of vendor lock in. Therefore, you are losing customers by not offering a data export option.
However, you don't want to be "helping" the competition by making the data transfer process trivial for your customers.
In an ideal world, customers should be free to leave with their data and you should make them stay not because you own their data but because you are the best. However, that might not be the best decision business-wise.
What's your take on this?