ולא זכר שר המשקים את יוסף – לא הזכירו בפה אל פרעה מיד בצאתו כמו שבקש ממנו יוסף כי אם זכרתני אתך, ולכך וישכחהו – בלב
The Chief Butler did not remember Yoseph: He didn’t mention him before Pharaoh immediately when he was freed, as Yoseph requested when he said “you should remember me,” and therefore “he forgot him” even in his heart. — Hizikuni
אמר להם יהודה המתינו לזקן עד שתיכלה הפת מן הבית
Yehuda told them let us wait to approach The Elder until all the bread in the house is finished. — Bereshit Rabba
The Chief Butler is often considered the chief ingrate in the Torah. When he is suffering in prison and bewildered by a troubling dream, Yoseph cheers him by interpreting his troubling dream and informing him that he will soon be released. All Yoseph asks for in return is that the Chief Butler should plead his case before Pharaoh and get him released as well. But the Chief Butler never fulfills this promise and promptly forgets all about Yoseph, at least until he has no choice but to recall him. It appears that as soon as he had no further use for Yoseph, he cast him aside.
But many commentators, including the Hizkuni quoted above, actually explain that when he was released he did fully intend to bring up Yoseph. He just never did so, and then he forgot. It seems to me that he was waiting on the optimal time. After all, Pharaoh was scary. He had once already thrown the Chief Butler into the dungeon and killed his friend, the Chief Baker. Mentioning a prisoner at the wrong time could be catastrophic. Best to wait until Pharaoh is in a good mood. But that opportune time never came, and Yoseph stayed in jail. Eventually, the Chief Butler stopped looking for opportunities and, some time after that, he forgot Yoseph entirely.
Whether he has good intentions or not, the Chief Butler failed Yoseph in the end. He pushed off the meeting, and by doing so he ensured it wouldn’t happen. In fact, Rashi and Hizkuni both imply that as soon as he did not meet with Pharaoh on the first day, it was inevitable he would forget Yoseph. Any delay was a sin.
There is a second person in the parasha who also pushed off a painful meeting for an opportune time. Yoseph told the brothers they could never come back to him without Binyamin. Although, Reuven tried and failed to broach the issue with Yaakov immediately, Bereshit Rabba says Yehuda specifically advised the other brothers not to act or say anything to Yaakov until the food ran out. Only then would it be an opportune time to request Binyamin go down to Egypt with them, for what other choice Yaakov have but to do whatever it took to get food? Binyamin and everyone else could starve in Canaan. Or he could go down to Egypt with the brothers, and maybe he would live. Yehuda’s plan worked beautifully, and he did indeed convince his father to choose the right course of action.
So how is it that two people made plans to push off an uncomfortable meeting, and in one case, it is cowardice, and in the other wisdom? There are often times when the Sages tell us that one should hold off on doing things with the usual alacrity, and instead wait for the opportune time. An example of this is the advice of R Shimon ben Elazar in Pirkei Avot not to immediately attempt to appease someone who is angry, or to immediately console a mourner before the funeral. But when one does hold off doing something at an inappropriate time, they need to have a definite appropriate time in mind.
Yehuda knew that he would have no luck approaching his father immediately, but he knew that the food would run out, and he would be able to argue his case. Angry people cool off, and mourners are eventually ready for consolation. But the Chief Butler never made a plan to approach Pharaoh, except to wait for when the circumstances were exactly conducive to it. That moment might never have arrived. If it did arrive, he might not notice it without a clear sign for himself. That’s why it was clear that when he didn’t bring up Yoseph immediately, he wasn’t going to bring him up at all. Without a plan for action, he may as well be the ingrate he is always pictured being.