u/Brother-Cane

The actual text of the Shilelagh spell states that, "For the duration, you can use your spellcasting ability instead of Strength for the attack and damage rolls ..."

It does not say that you must, but rather that you can. Nevertheless, on reddit and elsewhere, people assume that you are required to use said spellcasting ability. This makes no sense given the dissection of wording devoted to other spells.

Can anyone offer an explanation for this?

I've noticed that a lot of DMs just aren't aware of cheap and free ways to improve immersion, especially in the days of the internet:

• Some shot bottles have shapes that make for perfect potion stand-ins.
• There are online apps which can create the fonts and borders useful in making your letters of recommendation and decrees look close enough to the official things for gameplay.
• Giving maps and old messages the look of being older is simple with putting the finished product in wet coffee grounds for a while before drying and cleaning it off. A lit and blown out match can be used to give a paper the look that it was salvaged from a fire.
• If one is willing to put in the time, libraries offer all sorts of music that one can use for mood.
• One can buy or download pictures from a National Geographic with articles about ruins, tombs and treasure hoards for an effective visual impact.
• Tattered old books acquired for pennies at a Book Fair can stand in for old tomes, especially when the title has been worn off.
• Occult symbols for what the characters see upon breaking into the cult's headquarters can be found online with ease.

Both versions of Simulacrum state that it "... uses the statistics of the creature it duplicates."

As the rules make it impossible for the creature to restore spell slots, how do you rule a Wizard's simulacrum? Does it have the same prepared spells as already prepared by the wizard being replicated or do you give the player a one-time chance to prepare a selection of spells?