[Fishysoup]

The classification is done because rogue planets etc. tell us things about the process of solar system and planetary formation. Yeah nature tends to have a continuum of things, but the classifications are primarily used as place holders so that people know what everyone's talking about.

[kazinator]

Since stars form in explosive events, it seems painfully obvious that some of the shit that comes flying out does not stick around, and that it could be planet sized/shaped.

[jointpdf]

Stars are formed in nebulas of gas and dust via gravitational collapse (accretion).

The remaining gas and dust that is swirling around the star flattens out into a disk (because of angular momentum). Planets gradually form in this disk, again via accretion (snowball effect).

https://en.m.wikipedia.org/wiki/Protoplanetary_disk

https://en.m.wikipedia.org/wiki/Accretion_(astrophysics)