Question: Why aren’t we strict by Shabbos candles to not light from one candle to another just as we are stringent to not light Chanukah candles from one candle to another?
A. The Rema in Orach Chaim 674:1 says we have a custom to be strict by Chanukah candles to not light them from one candle to another since the main mitzvah is with one candle and the rest aren’t totally for the mitzvah (rather only to glorify the mitzvah.)
B. Halachically one only needs one candle for Shabbos candles we light at least two as a reminder of Shamor vizachor, keeping and remembering the Shabbos which refers to the negative and positive mitzvos associated with Shabbos.
C. Shabbos candles were enacted for Shalom Bayis so it would be easy to see in the house and make Shabbos more enjoyable.
D. One can light from one candle to another if there is an equal level of mitzvah for example two roommates on the first night of Chanukah can each light from each other’s candle.
Answer: Each Shabbos candle makes it brighter in the room and is more directly adding to the mitzvah of delighting in Shabbos so they each have equal Mitzvah status and can light one from the other even though it is enough with one. But by Chanukah there is nothing integrally being enhanced to the mitzvah by each extra candle it is just a way to beautify the mitzvah more by lighting an additional candle each day therefore one shouldn’t light from one candle to the other (See Dirshu footnote 7.)