There are a few reasons for not using DC until the last metre or so.
First of all, you want to avoid having multiple wiring systems in one building. Wiring a building for 110V alone is expensive enough (both initially and later during maintenance). In the vast majority of situations, you are going to have to pick one or the other.
So: AC or DC? Either way, you need to be able to run high power appliances (e.g. a 2000W kettle), and to keep losses in your cables low you need to use as high a voltage as possible, which will keep the required current as low as possible. So either way, in a realistic scenario, you need to retain the high voltages (110/230V) that we currently use.
When you require high power / high voltages, AC is a better solution. It is easier to switch (your kettle switch will burn out much more quickly while trying to interrupt a high current DC supply than it will interrupting an AC supply that crosses 0V 100 times per second). Overload devices work more reliably with AC for the same reason (which makes your house less likely to burn down). AC also makes it much easier to transform voltage levels - you just use an inductor or two. DC requires relatively complex electronics. DC distribution is also more complicated since the the distribution network and everything attached to it has parasitic (or deliberate) inductance and changes in load produce voltage spikes
There's nothing to stop you from installing a DC system in your house, but I think you would find it significantly less practical than you had imagined
Minor nitpick: relatively few quality solar panels generate
12Vdc. Most generate around 40V
First of all, you want to avoid having multiple wiring systems in one building. Wiring a building for 110V alone is expensive enough (both initially and later during maintenance). In the vast majority of situations, you are going to have to pick one or the other.
So: AC or DC? Either way, you need to be able to run high power appliances (e.g. a 2000W kettle), and to keep losses in your cables low you need to use as high a voltage as possible, which will keep the required current as low as possible. So either way, in a realistic scenario, you need to retain the high voltages (110/230V) that we currently use.
When you require high power / high voltages, AC is a better solution. It is easier to switch (your kettle switch will burn out much more quickly while trying to interrupt a high current DC supply than it will interrupting an AC supply that crosses 0V 100 times per second). Overload devices work more reliably with AC for the same reason (which makes your house less likely to burn down). AC also makes it much easier to transform voltage levels - you just use an inductor or two. DC requires relatively complex electronics. DC distribution is also more complicated since the the distribution network and everything attached to it has parasitic (or deliberate) inductance and changes in load produce voltage spikes
There's nothing to stop you from installing a DC system in your house, but I think you would find it significantly less practical than you had imagined
Minor nitpick: relatively few quality solar panels generate 12Vdc. Most generate around 40V