Many real estate investors perform a deal called 'subject to the existing mortgage' when purchasing homes from other people. What occurs is the homeowner Quitclaim Deeds their property into another's possession, without refinancing the loan into another's name. We have investors that have done this 100s of times personally and the lender has never called the loan 'due in full'. In short, the bank doesn't care about the transfer as long as they keep receiving on-time payments.
NOTE: This does not apply to second mortgages or second lien position loans that use the home as a secured asset because these positions are unlikely to get paid. Further, these transfers can cost more to resolve than a first lien position mortgage holder, so a 'balloon payment' clause will often come into effect from these loan types.