1) The Rashbam (131b, DH Lo) writes that the reason why the husband intended to make her a caretaker was so that his children should pay her respect. The children see that their father put her in charge of all his property and their livelihood now depends on the way she applies her discretion. This makes the children subject to the mother. The husband has done more than simply make his wife a caretaker. He has granted to her financial influence.

2) I want to elaborate a little on the above idea and suggest that the husband does a Mitzvah when he makes his wife a "caretaker" in this way. As we saw, the Rashbam writes that the man wants his children to give Kavod to their mother. This means that the husband also thereby indirectly gives Kavod to his wife. This is a big Mitzvah, as the Gemara in Yevamos (62b) states that if a husband honors his wife more than he honors his own body, he merits the verse, "And you shall know that your tent is at peace" (Tosfos there, DH Chayav, writes that one who honors his wife may call out and Hash-m will answer him; see Yevamos 63a). This Mitzvah is mentioned by the Rambam in Hilchos Ishus 15:19: "The Sages also commanded that a man should honor his wife more than his own body."

I contend that the husband who made his wife a "caretaker" is giving her more honor than his own body, because instead of the children being financially subject to him, they are now subject to her.

3) There are other Mitzvos that the husband fulfills when he gives a present to his wife:

We can learn from the words of the Rashbam (131b, DH Lo), "Kedei she'Yechalku Lah Banav Kavod," that apart from the Kavod that the wife receives, there is also an additional advantage that the children honor her and thereby do a Mitzvah. The Rashbam writes "Banav," his sons. The Rambam (Hilchos Zechiyah u'Matanah 6:4) writes that this refers both to sons that he has from her or those from another wife. If they are also her sons, then obviously they are doing a Torah Mitzvah when they honor her. Even if they are his sons and not her's, they also have a Mitzvah to honor their step-mother, as Kesubos 103a states that there is a Mitzvah to honor one's father's wife.

If the husband would merely say that he is making his wife a caretaker, this would not stress the fact that she now has the discretion to do with the property as she wishes, and the children would not feel the importance of the wife if she is not looked upon as the owner but merely as a business manager. Now that he called it a present, they honor her as the mother or step-mother, which is a bigger Mitzvah.

Kol Tuv,

Dovid Bloom