There’s a couple of reasons straws might be convenient or even necessary:

• You have a disability that causes movement problems like shaking
• Limited neck/shoulder/arm mobility or a swollen lip (The latter makes it hard to get a proper seal)
• You wear lipstick or other makeup that could get washed away
• Your edibles were too strong
• You can build containers that don’t spill when they fall over

(Edit: Add text at the beginning instead of just throwing a list out there)