I have been woodworking for 30 or 40 years and biscuits are a relative
newcomer to the craft. Folks have been edge gluing with white glue,
and previously animal glues, for generations by producing good
straight joints and clamping them up. I do own, and use, a biscuit
joiner and find it very useful in helping align the edges of a glue
up. There are tons of "studies" regarding the strength advantages of
biscuits and they do undoubtedly enhance a glue up. But they are more
handy than essential.
BTW, Biscuits do not guarantee a flat table top. You still have to
pre-fit, fiddle, glue and then fiddle to get it perfect.
Then sand an little.