"Best Practice" typically dictates LPU (least privileged user)...but you are correct (as is ETL and Joe so +1) that people rarely follow this model.
Most recommendations are to do as you say...create 2 accounts and not share those accounts with others. One account shouldn't have admin rights on even the local workstation you are using in theory, but again who follows that rule, especially with UAC these days (which in theory should be enabled).
There are multiple factors in why you want to go this route though. You have to factor security, convenience, corp policy, regulatory restrictions (if any), risk, etc.
Domain Admins and
Administrators domain level groups nice and clean with minimal accounts is always a good idea. But don't simply share common domain admin accounts if you can avoid it. Otherwise there's a risk of someone doing something and then finger pointing between sysadmins of "it wasn't me that used that account". Better to have individual accounts or use something like CyberArk EPA to audit it correctly.
Also on these lines, your
Schema Admins group should always be EMPTY unless you are making a change to the schema and then you put the account in, make the change, and remove the account. The same could be said for
Enterprise Admins especially in a single domain model.
You should also NOT allow privileged accounts to VPN into the network. Use a normal account and then elevate as required once inside.
Finally, you should use SCOM or Netwrix or some other method for auditing any privileged group and notify the appropriate group in IT whenever any of these group's members have changed. This will give you a heads up to say "wait a minute, why is so and so suddenly a Domain Admin?" etc.
At the end of the day there's a reason it's called "Best Practice" and not "Only Practice"...there are acceptable choices made by IT groups based on their own needs and philosophies on this. Some (like Joe said) are simply lazy...while others simply don't care because they aren't interested in plugging one security hole when there are hundreds already and daily fires to fight. However, now that you've read all of this, consider yourself one of the ones that will fight the good fight and do what you can to keep things secure. :)