According to Wikipedia, SimpleMDM doesn't provide "Device Lockdown" and "Expense Management", whereas there are some vendors provide all (all green in a row). [1]
Also as far as I know, SimpleMDM pricing[2] is not the cheapest in the market either, their feature set is similar to Mosyle's, but Mosyle's cheaper.[3]
Picking products based on feature checklists is how people end up buying horrible enterprise software, and then spend enormous resources trying to make it work. Doing everything implies not doing anything well.
SimpleMDM doesn't try to do everything, as the name implies, but instead they focus on doing what they do extremely well.
If you been in an enterprise RFP process, you will understand "Picking products based on feature checklists" is commonly being done to compare software products because if you don't provide the feature that your competitors provide, you are pretty much out of the competition.
Also as far as I know, SimpleMDM pricing[2] is not the cheapest in the market either, their feature set is similar to Mosyle's, but Mosyle's cheaper.[3]
[1:] https://en.wikipedia.org/wiki/List_of_Mobile_Device_Manageme...
[2]: https://simplemdm.com/pricing/
[3]: https://business.mosyle.com/pricing