Agree with you in one sense of being responsible for your own security, but by this logic I should keep all my money under the mattress instead of the bank, no?
More like "by this logic I should keep all my money under the mattress instead of in a jar in my cousin's pantry, no?"
Slack isn't a secure vault for data, it's a communications tool. They obviously have some amount of security but that's not their purpose, whereas a bank is intended to store money.
I think running your own IRC is a perfectly acceptable solution if you value your data.
Can you say the same about cloud services?
If you have great physical security at your home and don't trust the banks (e.g. their fee schedules), it might be a safer decision.
For most people, it's not.
They froze all accounts and they even threatened the population with opening the safe deposit boxes.
Big fan of customers having a way out and not have to trust the service provider.