אילו סיפק צרכינו במדבר ארבעים שנה
The Hagadah does not explain what needs where provided in the desert by HaShem that without them would have been life threatening.
Possibly, that the intention is to what is written in Parshas Savo:
דברים כט , ד וָאוֹלֵךְ אֶׁתְכֶׁם אַרְ בָעִׁים שָנָה בַמִׁדְבָר לֹא -בָלוּ שַלְמֹתֵיכֶׁם מֵעֲלֵיכֶׁם וְנַעַלְךָ לֹא-בָלְתָה מֵעַל רַגְלֶׁךָ :
“I have led you forty years in the desert, your garments have not worn out on you and your shoes have not worn out on your feet”
Gemara Berachos (60b) cites that in the morning blessings when one puts on shoes then one says the blessing acknowledging that He supplies us with all one’s needs. How does that relate to putting on one’s shoes?
Possibly we can explain according to the Gemara Shabbos 129a, that a person should always sell all one’s possessions to acquire shoes, and Rashbam explains that is a disgrace to a person to go bare-footed.
It is a general principal that coldness enters through the feet. Therefore, shoes are necessary for the health of the complete body.
Thus, we can now explain the morning blessing that putting on one’s shoes it is as if one has all one’s basic needs and thus so recites the blessing.
Therefore, the Hagadah also has a similar explanation. HaShem took care that the shoes never worn old. Thus, the Jews in the desert did not have to sell everything in order to acquire new shoes (high demand in the desert with low supply). Thus, the Hagadah states that all our needs were supplied.
Another idea is providing by contrasting the verse in Parshas Ekev:
ח, ד שִׁ מְלָתְךָ לֹא בָלְתָה מֵעָלֶׁיךָ וְרַגְלְךָ לֹא בָצֵקָה זֶׁה אַרְ בָעִׁים שָנָה :
In that verse, שמלה (clothing) is in the singular, whereas in Parshas Savo the same word is written in plural. It is possible to explain each place provides a broader view of the miracle. When the Torah writes in the singular implies that not even one garment in the entire wardroom of the nation worn out. And when the Torah wrote in the plural, this indicated that even if a person always wore the same garment, it never worn out. Even though the verse in Parshas Savo referred to clothes in the plural, it referred to the shoes in singular. The two shoes are a unit and one does not have a normal benefit from the use of only one shoe.
