The issue is the 5th amendment in the bill of rights, which basically says you can't be forced to testify against yourself. (That includes providing password to your devices and/or accounts) Just because someone has a warrant to search your house for physical evidence, doesn't mean they have a warrant to search you brain for thoughts and memories.
Take for example an off-shore bank account. With a search warrant for your house, they can't put you in front of your computer and force you to log into your bank's website. Instead they would also need to get a warrant for the bank and get your records that way. (although, depending on the country, the bank isn't required to comply)
However, now that our physical bodies are our passwords (fingers/faces), it is an area of the law that should be defined better. Is forcing someone to look into their Face ID camera or put their finger on a Touch ID scanner considered forcing them to testify against themselves? If so, and I believe it is, it is unconstitutional.