There is a lot of discussion about inside/outside on the Empire.
Trees evolved stuck in the ground not able to move, so they expect a certain combination of climate, dark/light, rain/dry, humidity, air motion, etc., and when they don't get what they evolved in, they get unhappy. None of them evolved filtering sunlight through glass, with weak light from indoor lighting, with pretty dry air, etc.
Some, like sageretia, should be brought in when the weather outside is colder than where they evolved, but trees don't read thermostats and what seems cold to us just seems like fresh air to most of them.
You can imitate outdoor sun with grow lights but you would have to imitate outdoor darkness by turning off the lights at night and having the tree be in pretty much complete dark every night. That is unpractical for most of us, and the easiest way to supply the right light cycle is put it outside. Being inside stresses them and while they may last a while, they don't thrive. There are dozens and dozens of posts about trees kept inside, all of them are told take it outside, and none of them come back months later and say they kept the tree indoors anyway and now they tree is bursting forth with new growth. None.