Why do so many Shopify stores still send the same email to everyone?

I've been looking at email marketing workflows used by Shopify stores, and one thing stands out:

Many stores still send identical campaigns to their entire customer list.

Someone who purchased yesterday gets the same email as someone who hasn't visited in six months.

Is the biggest challenge:

• Creating good content?
• Segmentation?
• Lack of time?
• Existing tools being too complicated?

Curious to hear how other merchants approach this Or if There is some post around this conversation. Happy to go through that.