Rain cycling pants are designed as a protective shell that you layer over your regular padded shorts or tights, so you still get the chamois comfort from whatever you're wearing underneath. Think of them as a rain jacket for your legs—they keep you dry but aren't meant to be worn alone against your skin.
They're most worthwhile if you regularly commute in wet weather, tour through unpredictable conditions, or want emergency rain protection on long bikepacking trips. If you only occasionally get caught in a drizzle, you might not need them.
The trade-off is breathability. Even the best waterproof fabrics trap some heat and moisture, so you can feel clammy during hard efforts. They also add bulk and can flap in the wind. For most recreational riders, a good pair of bib shorts or tights with a rain jacket is sufficient—save the rain pants for when staying dry really matters, like a cold, wet commute where arriving soaked isn't an option.