I agree in part. There are many "mini" trees and shrubs. And depending on what zone the plant can survive in will depend if it can survie outside all winter in a container. I assume you are talking about surviving outside. If you keep a plant in a container all winter you need a plant that can tolerate colder conditions that you zone limits. For example if you live in zone 6, then the plant that you are keeping outside should be able to tolerate zone 5 or less. Location ( micro climates ) also plays a important factor in what will survive.
Plants labled as Mini, may not always be mini for long. Recent sales of mini conifers for the west coast, sometimes are just baby plants that will eventually get much too big for a container. Best to do your homework before you buy.
I do agree 100% that containers are the answer to probelms that gardeners have with limited space to plant. If you do a search on the hypertufa gallery your will find many unique handmade containers that include all types of plants - just right for small space gardening ---Thanks for your posting