How do I allow the Rogue opportunities to be stealthy with a Druid in the party?

My party is currently level 6, and consists of a Halfling Rogue, Human Druid, Halfling Barbarian, and Half-Elf Monk. They’re all excellent players who play tactically and know their class well. I’m currently running into a problem with the Rogue and the Druid.

My Rogue has Expertise in Stealth (+10 at this level) and a Cloak of Elvenkind. This means that her minimum roll (barring four 1s because they’re a Halfling) on a Stealth check is a 12, and her average roll is around a 25. Even on a minimum roll, most NPCs will not be able to see her (and in a few levels that will extend to all NPCs).

However, the party’s current methodology is to have the Druid do the sneaking instead of the Rogue. Their reasoning is that even though it’s highly unlikely that the Rogue will get caught, if she does get caught then really bad things happen – the enemy will know they’re being spied on, the Rogue gets captured, etc. However, the Druid is spying in the form of a rat, spider, owl, or other sneaky animal, so if a bandit spots a bat they probably won’t think much of it. Additionally, the druid will have a much easier time escaping a secure location (say, by summoning 8 Giant Badgers and then Wild Shaping into a spider).

Here’s my problem with this: I see “Being Sneaky” as a core part of a Rogue’s class identity, and the player has invested a lot of resources (proficiency, expertise, and an attuned item) into being sneaky. I try to give all of my players a chance to live out their class identity: The Barbarian gets to hulk out and smash things, the Druid gets to save Dryads and heal cursed forests, the monk gets to take people down bare-handed, etc. I want to have at least some opportunities for the Rogue to get to experience this key feature of their class by sneaking into a secure location or scouting out an enemy party.

How can I design stealth-based encounters or challenges so that the Rogue will be a better choice than the Druid?