why not buy with online exchanges?

I prefer the security and anonymity of OTC and ATMs.
I learned my lesson with MtGox. Lost 50 coins. Never again.
When I acquire coins, they go straight into offline cold storage, mostly paper wallets, although I do keep a small amount (less than 5 coins) in a Trezor for convenience.
I don't ever want to expose my coins to the internet. I also resent nosiness. Anonymity is the cornerstone of freedom.
Yes, ATM fees are usually higher than exchange fees but when you consider the cost of transferring fiat currency and the total lack of anonymity of online exchanges, it's a small price to pay.
Whenever I have the chance to acquire coins for cash, anonymously, it's a bonus. I've met other Bitcoiners at meetups who I only know on a first name basis. I've also bought coins from storefront gold and coin dealers without divulging my name. They get their cash, I get my coins, no names required.
Did your ATM let you withdraw 2 $2.5k transactions anonymously (without ID) a few weeks ago? I assumed you must have provided ID scans to get that kind of limit allowed.
You can get that much out of an ATM in Canada?

No problem. Some machines allow up to $10k per day to stay within AML limits.
My local ATM allows up to $5k per day but I had to split it into 2 $2.5k transactions.
Paid me all in brownies ($100 bills) after only 2 confirmations. Fast, clean and simple.