Buy, Rehab, Rent, Refinance, Repeat - got them all with questions on refinance/repeat

[Pixel Rogue]

Been in apartment rentals for about 20 years. Mortgages are all below 4.5% - no intention of changing those. Have a few arms due in about 5 years..those I will finance to fixed rate as rates lower. 

Buy - Rehab - Rent - that has been the bulk of the work. I am not clearly following the the refinance bit. I have refinanced (rarely mind you as there are costs that take years to recoup on a refi) and am happy to see equity build as the mortgage shrinks. It is my understanding that people refinance and then use those funds other ways (personal living, investing, some to buy another property) as a means to minimize tax obligation. To me I'm not seeing this as clearly as those who are deep into the BRRRR philosophy.

ELI5

Also, the rehab part gets old after a while...rehab and maintenance never ends.