A floating mortgage gives the flexibility to make lump sum payments or increase the mortgage instalment, without any penalty or break fees that can apply to fixed rate mortgages.
For many people this part of their mortgage is the part that allows them to significantly accelerate mortgage payments and so get debt repaid faster.
However floating rate mortgages are exposed to any increase in interest rates and if those rate increases are significant the floating mortgage instalment can also increase significantly.
For this reason many people will have the major portion of their mortgage fixed and just a small portion floating.
For many the flexibility of a floating mortgage far outweighs the risks of interest rate volatility.