It varies slightly depending upon the lectionary but using the RCL as an example:
Every Sunday has 3 readings with the following characteristics:
1st reading - somehow is thematically related to the Gospel except in Lent when it gives an overview of salvation history (Old Testament except iin the Easter season when it is from Acts)
responsorial psalm - a psalm that relates to the Gospel or the first reading
epistle - a semi-continuous reading of an epistle; independent of other readings
Gospel:- a reading for the Gospel emphasized during the particular year; generally in sequence
Net result: one rarely studies a passage in isolation - one or more of the other readings also comes into play.
In addition, one usually makes reference to the previous week's readings and the upcoming week. So one reads in the context of a dozen passages of scripture.
It is my impression based on the forum and Logos functions (don't get mad - it isn't all functions) that the majority of non-lectionary Bible studies starts with a single passage - to which parallels and cross-references are often added, along with proof-texts for the points made in the study.
Several things over the past year have led me to believe that many on the forums don't really understand my fascination with lectionaries. It's best summarized as mult-text studies vs. single-text studies. I hope this helps you understand why.