Mini-USB vs micro-USB vs USB-type C.. innovation or just marketing?

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It appears in the past 10 years mobile phone connectors have changed no less than three times: - Some of the phone manufacturers of 2005-2006 started giving up proprietary connectors in favor of the same Mini-USB connector used on digital cameras and GPS devices -then, about in 2009 devices using the micro-USB port became the most frequent. It was great that by adopting it as a standard, you could use any charger for your phone, regardless of its brand. So for instance if you had a HTC at home and a Samsung at work, you needn't carry the charger with you, but could use it for both devices -now, a new change is under way, at least on some high-end devices. First there was the Microsoft Lumia 950, then the HTC 10, or the (now withdrawn) Samsung Note 7. Apart for the fact the USB type C is reversible, so you can insert it without caring it's upwards or downwards, I see no practical purpose for these changes. Is there really any space saving? Seriously, the connector is really small in any of its form factors. So what's the purpose of the change?