Example GitHub - nielsfaber/scheduler-card: HA Lovelace card for control of scheduler entities
Already exists:
You have to automate what actions you want when the schedule turns on.
If that is not enough for you use the third party card you linked to.
This will be convenient for those people who do not want to learn automation and scripts. This will lower the barrier to entry for beginners and allow beginners to gradually learn automation, templates, scripts and blueprints.
Not everyone who wants to try building a smart home wants to learn programming.
And try asking the developer to submit it to the core. That is beyond HA’s control and the developer may not want to. As a third party resource they can release updates whenever they want to rather than waiting for core updates.