The Chofetz Chaim zt”l explains that some people’s entire lives revolve around going to work. And they only go to work in order to earn a livelihood so that they have bread to eat. And they only eat so that they have energy to go to work. And so it goes, around and around. Their entire lives revolve around working and eating. Regarding such people, Dovid Hamelech said (Tehillim 12:9): “Wicked men circle around as they walk.” A wicked man’s life revolves solely around his own physical needs.
Thus, the pasuk means that “man should not live on bread alone.” A person’s life should not revolve around eating. Rather, a person should live to fulfill the will of Hashem, to learn Torah and keep mitzvos.
Similarly, the Gemara (Beitzah 16A) says: “How foolish are the Babylonians who eat bread with bread.” Sefer Bais Shmuel Acharon (Parshas Shemini) explains that they ate bread in order to have the energy to eat more bread. Their lives revolved around eating rather than on any higher purpose.
וַיְעַנְּךָ וַיַּרְ עִבֶךָ וַיַּאֲכִלְךָ אֶת הַמָּן וגו' כִּי לֹא עַל הַלֶּחֶם לְבַדּוֹ יִחְיֶה הָאָדָם כִּי עַל כָּל מוֹצָא פִי ה' יִחְיֶה הָאָדָם (ח, ג)
And He afflicted you and let you go hungry, and he fed you with mann... that man does not live by bread alone, but rather by, whatever comes forth from the mouth of Hashem a man lives. (8:3)
ת תֹּאכַל בָּהּ לֶחֶם לֹא תֶחְסַר כֹּל בָּהּ וגו' (ח, ט)
אֶרֶ ץ אֲשֶ ׁר לֹא בְמִ סְ כֵּנ
A land in which you will eat bread without scarcity, you will lack nothing... (8:9)
